Can Drinking Water Really Improve Academic Performance?
“Can something as simple as drinking water actually change your grades?” Many of us have experienced that moment in class when a small sip of water makes our mind feel a little clearer. But how much of that feeling is backed by science? Surprisingly, not many people know the answer. And in some school environments, where students have limited access to safe drinking water in the first place, children may be learning while mildly dehydrated without even realizing it.
So, does staying hydrated really affect learning? To answer that question, researchers conducted a randomized controlled trial (RCT) involving 279 primary school students in Zambia. One group received personal water bottles and could drink freely throughout the day. The other group continued their usual routine, where access to water was extremely limited. The study then compared how the two groups performed on a series of cognitive tests.
The results aren’t as simple as you might expect—but that’s exactly what makes them fascinating. In the sections ahead, we’ll carefully unpack the science behind hydration and learning, and what this study really tells us about the link between water and cognitive performance.
The Link Between Dehydration and Brain Function
Our brain is far more sensitive to water balance than we might imagine. Research shows that losing just 1–2% of the body’s water can subtly impair key cognitive functions—attention, concentration, processing speed, and even mood stability. These effects occur in adults, but children are even more vulnerable because of their smaller body size and higher metabolic rate.
What makes dehydration particularly tricky is that mild dehydration rarely comes with clear symptoms. Not feeling thirsty doesn’t mean your brain is functioning at its best. In fact, cognitive performance can quietly decline long before the body sends any obvious warning signs.
So what does the global school environment look like? Around the world, many schools still lack something as basic as reliable access to drinking water during class. According to reports by UNICEF, nearly half of schools in low-resource countries cannot provide students with enough water throughout the school day. Broken water systems, distant water sources, or simply the lack of financial capacity to secure a stable supply all contribute to this issue. As a result, millions of children spend their school hours in a state of chronic mild dehydration while trying to learn.
Of course, dehydration doesn’t necessarily cause a dramatic drop in academic performance right away. But when attention becomes a little harder to sustain, concentration breaks more easily, and thinking slows down—even slightly—those small differences can accumulate day after day. Over time, they can affect the overall quality of learning. That’s why the question “Does drinking water influence learning?” isn’t just a matter of health. It’s an important issue of educational equity—because something as basic as access to clean water can shape a child’s ability to learn on a daily basis.
The RCT Conducted in Zambia
To explore this issue more deeply, the research team chose five primary schools in Chipata, one of the regions in Zambia where access to clean water is particularly limited. In many of these communities, schools do not have a safe water source within 500 meters. As a result, children often go from morning until early afternoon with little or no opportunity to drink water. In other words, attending class while mildly dehydrated is not an exception for these students—it is the everyday reality of their learning environment.
To examine whether simply allowing children to drink water freely can improve their cognitive performance, the researchers conducted a randomized controlled trial (RCT) involving 279 students in grades 3 to 6. An RCT is considered one of the most rigorous methods for establishing causal relationships in fields like medicine and education, making it a highly reliable way to test this question.
The procedure was simple, yet highly precise.
The students were randomly assigned to one of two groups:
Intervention group: Students received personal water bottles and were allowed to drink freely throughout the day.
Control group: Students continued with the school’s usual conditions, where access to drinking water was extremely limited—and for many, almost nonexistent.
The students were assigned to one of these two groups at random.
To objectively measure hydration levels, researchers collected urine samples from all participants twice—once in the morning and once in the afternoon. They used urine specific gravity (Usg) as an indicator of dehydration. This allowed them to accurately compare how dehydrated the children actually were and how much their hydration status changed when water was provided.
In the afternoon, the students also completed six different cognitive tests measuring skills such as short-term memory, visual attention, concentration, visual processing, and visuomotor ability. These assessments were essential not only for detecting changes in overall performance, but also for identifying which specific cognitive functions are most sensitive to hydration status.
What makes this study particularly compelling is that it didn’t rely on self-reported feelings or vague impressions. Instead, it combined physiological data (urine measurements) with behavioral data (cognitive test performance). In other words, the researchers designed the experiment to directly examine how a physical state—dehydration—translates into changes in learning-related behaviors. It’s a carefully structured approach that allows for a clear investigation of cause and effect.
Hydration Levels Improved Dramatically
One of the most striking findings of the study was how significantly the children’s physical condition changed depending on whether they had access to water. By the morning, 42% of all students were already in a dehydrated state—a figure that is not unusual in schools where drinking water is scarce. But as the day progressed, the difference between the two groups became even more pronounced.
In the control group, where children had almost no access to drinking water, the afternoon dehydration rate climbed all the way to 67%. Because they were unable to drink during classes or break times, their dehydration worsened steadily as the hours passed. In schools without any water source at all, this percentage tended to be even higher—clearly illustrating how profoundly the availability of water affects children’s physical condition.
In contrast, the change observed in the intervention group—the children who had free access to water bottles—was remarkably clear. Although their morning dehydration levels were nearly the same as the control group’s, their dehydration rate dropped to just 10% by the afternoon. In other words, simply providing an environment where children could drink freely allowed those who had been mildly dehydrated to return quickly to a normal hydration state. Given the hot and dry conditions of Zambia—average temperatures around 31°C with 17% humidity—this difference wasn’t just meaningful; it was potentially life-preserving.
What makes the findings even more compelling is how clearly the differences were reflected in the urine specific gravity (Usg) measurements. In the control group, Usg values increased over time, indicating that dehydration was steadily worsening. In contrast, the intervention group showed a decrease in Usg, demonstrating that their bodies were effectively rehydrating. This means the improvement wasn’t just a matter of “feeling more hydrated”—the children’s physiological state was objectively better. The data provides clear scientific evidence that access to water directly improved their hydration levels.
These findings show that even within a single day, a child’s physical condition can change dramatically depending on whether they have access to water. This simple but powerful fact is the first major takeaway from the study.
But the Cognitive Test Results “Barely Changed”
What makes the study even more intriguing is that—despite such a dramatic improvement in hydration—the answer to the question “Did their cognitive test scores improve as well?” was surprisingly no. In the afternoon, the research team administered six different assessments, including tests of short-term memory, visual attention, visual processing, digit span (recalling numbers in reverse order), and line-drawing tasks. These were designed to measure the children’s day-to-day learning abilities with precision. However, the conclusion was clear: most of the cognitive tests showed no significant differences between the groups.
The only test that showed noticeable improvement was the direct image difference test, which measures visual attention. Here, the intervention group scored slightly higher (p = 0.05). However, this effect was not strong enough to be considered clearly statistically significant, meaning it cannot be confidently described as a substantial improvement. For the other assessments—including short-term memory (digit recall), visual memory (indirect image difference), and visuomotor skills (line trace)—there were virtually no differences between the intervention and control groups.
In other words, even though the children’s hydration levels changed dramatically, their test scores remained nearly the same—a result that was, in some ways, quite unexpected.
So why did this gap occur?
The research paper offers several important possibilities.
One explanation is that a single day of improved hydration is not enough to reverse chronic dehydration. If children are mildly dehydrated on a daily basis, drinking water for just one day may not immediately optimize brain function. The effects of long-term dehydration may take longer to resolve than a short intervention can provide.
Another possibility is that the cognitive tests themselves were originally developed for children in United Kingdom and Israel, which means cultural differences or unfamiliarity with the testing style may have influenced the results. In fact, the study noted that in some cases, different versions of the same test produced different scores, suggesting that test design may have affected performance.
What’s even more interesting is that giving children free access to water led a few of them to over-hydrate, resulting in unusually low urine specific gravity. Excessive water intake can affect cognitive performance in a different way, and the paper points out that this may also have influenced the scores.
In short, while hydration clearly matters, it does not necessarily translate into instant improvements in academic performance. The study reveals a more nuanced reality: water is essential, but the relationship between hydration and learning is not as simple as “drink water and your grades immediately improve.”
Hydration Is the Foundation of a Healthy Learning Environment
At this point, some readers might wonder:
“If drinking water doesn’t improve test scores, does hydration even matter for learning?” In reality, the study suggests the opposite.
Hydration may not be a quick fix that instantly boosts grades, but it is a fundamental environmental condition that supports learning. In other words, water is not a performance enhancer—it’s part of the basic infrastructure that allows children to learn effectively in the first place.
First, the researchers point out that one likely reason for the minimal change in cognitive scores—despite the dramatic improvement in hydration—is the possibility of chronic dehydration. If children are living in a mildly dehydrated state on a daily basis, drinking enough water for just a single day may not be enough for their brains to perform at their highest potential.
Instead, meaningful improvements in learning may only become visible when access to water is improved consistently over the long term, allowing the brain to gradually recover from the cumulative effects of chronic dehydration.
Second, the study does not simply show that “drinking water didn’t improve test scores.”
Rather, it clearly demonstrates how severely dehydration can worsen when children lack access to water—and this is a far more important issue for schools. Dehydration is known to cause reduced attention, increased fatigue, lapses in concentration, and irritability. These small, everyday impairments accumulate over time, and the cumulative effect can unquestionably influence students’ learning attitudes, engagement, and overall comprehension.
Moreover, hydration matters not only for academic performance, but also for health, safety, and educational equity. A classroom environment where children cannot access clean drinking water—and are forced to learn while thirsty—is fundamentally unacceptable. This issue is not about “drinking water to raise test scores.”
It is about ensuring that every child has a safe, supportive, and equitable environment in which to learn. Access to water is part of the basic educational infrastructure that should be guaranteed for all students.
The true value of this study lies precisely here.
Its significance is not in demonstrating any “instant boost” from hydration, but in scientifically revealing that the presence—or absence—of water shapes the very starting point of a child’s learning. That fundamental insight is what makes this research so important.
Water as the “Invisible Infrastructure” of Learning
This study offers a surprisingly nuanced answer to the simple question: “Does drinking water improve academic performance?” It’s true that allowing children to drink water for just one day did not produce dramatic gains in cognitive test scores. But that does not mean hydration is irrelevant to learning.
In fact, the results suggest the opposite:
the lack of access to water itself may be quietly undermining children’s ability to learn. Water may not instantly raise scores, but it functions as an invisible form of educational infrastructure—a basic condition that supports every child’s capacity to focus, participate, and thrive in the classroom.
Dehydration gradually affects attention, concentration, and even mood. These changes aren’t as immediately visible as test scores, but their accumulated impact can influence a child’s learning posture, engagement, and depth of understanding. Over the long term, they can shape the very foundation of academic performance. That is why hydration should not be seen as a “magic shortcut” that instantly boosts scores. Instead, it is an essential precondition for creating a learning environment where every child has the capacity to focus, participate, and grow.
The randomized controlled trial conducted in Zambia provides clear scientific evidence of this reality. Children who were able to drink freely throughout the day showed a substantial improvement in hydration, while those without access became increasingly dehydrated as the afternoon progressed. This growing “difference in physical condition” is a crucial signal—one that cannot be ignored when considering how learning builds day by day.
Ensuring access to water is, in many ways, ensuring the foundation of learning itself. Improving the quality of education requires more than blackboards and textbooks—it also demands attention to basic, essential infrastructure such as safe and sufficient drinking water. This study quietly reminds us that something as ordinary as water is, in fact, a vital element that supports every child’s ability to learn.
References
Trinies V, Chard AN, Mateo T, Freeman MC.
Effects of Water Provision and Hydration on Cognitive Function among Primary-School Pupils in Zambia: A Randomized Trial.
PLOS ONE, 2016. DOI: 10.1371/journal.pone.0150071