But what you might not know is that kids who stay topped up with water and fluids perform better in class.
The 'Children's Hydration Glass' developed by the Natural Hydration Council (NHC) in collaboration with the British Nutrition Foundation (BNF), aims to inform both parents and children on healthy hydration guidelines.
An infographic includes hydration guidance and advice on fluid consumption for children, whilst taking into account the impact that some drinks may have on dental health.
Research published in the latest issue of Complete Nutrition found that providing children with water at school significantly increased levels of visual memory and performance.
Dr Emma Derbyshire from Manchester Metropolitan University, who led the research, said: "This indicates that adequately hydrated children may perform better and be better behaved in school."
Bridget Benelam, Senior Nutrition Scientist at the BNF said "We know there is a lot of confusion about how much and what children should be drinking.
Water is a great choice to keep children hydrated, but other drinks like milk, juices and soft drinks can contribute too.
"It's just important to be aware of the calorie content of drinks and the potential impact on dental health so that parents and carers can help children to develop healthy drinking habits."
The amount of fluid a child needs depends on many factors including age, gender, weather and how much physical activity they get but generally they should aim to drink about 6-8 glasses of fluid per day (on top of the water provided by food in the diet).
Younger children need relatively small servings (e.g. 150ml per drink) and older children need larger servings (e.g. 250–300ml per drink).
Dr Derbyshire, said: "Simple measures, like the addition of a bottle of water to the school lunchbox or backpack by parents could help to reinforce healthy hydration habits in children."
Dr Derbyshire's top tips for keeping kids hydrated
1. Children should aim to have 6-8 drinks per day which should ideally be water. However, weak squash and diluted fruit juices are OK.
2. Put a bottle of water in lunchboxes as this is the fluid that the BNF advises drinking 'plenty of'.
3. Children should be encouraged to sip fluids at regular intervals throughout the day - a lot of children drink fluids at the end of the day when feelings of dehydration have already started to set in.
More information and a downloadable version of the 'Children's Hydration Glass' is available from www.naturalhydrationcouncil.org.uk.