This study from the University College London looked at the sleep habits of 11,000 kids between the ages of 3 to 7. It found that 3 year olds with irregular bedtimes tested lower on reading (3 year olds read?), math, and spatial awareness. By age 7, just the girls tested lower. Other research from Australia has shown that poor sleep is associated with lower math and literacy skills, as well as behavioral issues.
From ages 3 to 5, kids need about 11 to 12 hours of sleep… and 10 to 11 hours during elementary school. Sleep needs vary from kid to kid, but that’s the general rule.