Safe drinking water is essential for good academic performance and attendance at school. Clean water means less illness caused by unsanitary drinking water amongst students and teachers.
Easy access to water saves time previously used walking long distances to collect water; and can be used to water plants for food.
Sanitation is also essential for health reasons, building toilet blocks specifically allows girls to attend school who would otherwise have dropped out of school at puberty.
"For every $1 invested in water and sanitation, at least $4 is returned in increased productivity." - Hutton, World Health Organisation