Are Early School Start Times Harmful for Kindergarteners?

Source: Erika Varga/Pixabay

The relations between adolescent sleep patterns and school start times have been the subject of research studies going back to the late 1980s. When I started this blog in 2012, one of my first posts described a study linking start times to school achievement in middle- and high-schoolers. Over the years I have written about start times regularly, and most recently I wrote about the controversial Florida legislation that originally mandated later start times but was repealed and replaced by a bill that encourages but does not demand later times. As school districts across the country have become convinced that start times have been too early to allow sufficient sleep for adolescents, many have adjusted their times. The emphasis has predominantly been on harm caused to adolescents. To accommodate transportation logistics, many districts “flipped” bus schedules to have elementary schools start earliest since prepubertal children were thought to be able to get sufficient sleep even when they had to be at school very early.

Last month I had the privilege of attending the annual meeting of the Associated Professional Sleep Societies in Seattle. Most of the nearly 5,000 attendees and presenters were either members of the American Academy of Sleep Medicine, the American Society of Sleep Technologists, the Sleep Research Society, or representatives of companies that sell products relating to sleep.

Recent studies offer insights

Two presentations by authors from Purdue University and Seattle Children’s Hospital related to school start times for children in kindergarten caught my attention because relatively little research has been done with elementary students and even less with kindergarteners. In the first study, researchers used data from 11,877 kindergarteners and divided them into four school start time groups: <7:45; 7:46-8:15; 8:16-8:45; and >8:46. Children with the earliest start times went to bed 11 minutes earlier than those with the latest starts, but sleep opportunity was still 77 minutes less for the earliest starters because they had to get up so early on school days. The authors conclude that there is a large mismatch between their sleep needs at that age (around 11 hours) and the time available to sleep. Moreover, the likelihood of having breakfast was much lower for the earliest starters (53%) than for the other groups (63%; 75%; 77). Children attending the earliest-starting schools were disproportionately Black, and were more likely to attend a Title I school, have a family income below $30,000, and/or live in a rural area. These results support an argument I have made several times on this page and elsewhere that all schools should ideally start after 8:30 a.m. As years of studies by our lab group and those of many other sleep researchers have shown, many children from low-income homes, especially those of non-white race/ethnicity, exhibit sleep disparities that are related to mental health and academic performance. In 2011, I made the argument that sleep insufficiency was likely related to achievement gaps that have endured for decades even as many solutions, some large scale (e.g., Head Start) have been proposed and implemented.

In the second study, a sample of 7,940 children were followed for five years beginning in kindergarten. The researchers were interested in how childhood asthma related to start times. One year after kindergarten, the prevalence of asthma was 15.4%, just over 1 in 7 children. By year five, the prevalence had risen to 17.2%. After controlling for demographic factors (e.g., income and others), earlier school start time in kindergarten was a significant predictor of asthma at year four and five. Obviously, an early start time is not the only factor compromising sleep, and compromised sleep is not the only contributing factor for asthma. But finding any association with start time and asthma years later is troubling.

Rethinking school start times

Starting school later has been shown in many studies to allow adolescents to attain more sufficient sleep, and data are encouraging that the additional sleep is related to important outcomes including better mental health. Research with younger children was originally not done because it was thought that being pre-pubertal, their biological clocks were more aligned with going to bed and getting up early. As the research has trickled out, the results have been mixed. Studies such as the ones described here give us pause about assuming that early starts do no harm to young children. Other studies have yielded results that show no harm is done. Lisa Meltzer and colleagues, for example, reported that elementary-school children in their sample did not suffer from sleep loss or sleepiness two years after their schools began an hour earlier from around 9 a.m. to 8 a.m.

After I returned from Seattle, I came across an article describing new start times for Escambia County, Florida (Pensacola city and county schools). Six of seven high schools will start at 8:30 and one at 8:45. Middle schools will start between 8:45 and 9:25. Sixteen elementary schools will begin at 7:50, four at 7:35, and 12 will start at 7:10. I was alarmed at the times for elementary schools, especially those starting at 7:10. The National Sleep Foundation guidelines for sleep needs by age state that preschoolers (3-5) need 10-13 hours of sleep and school age children (6-13) need 9-11 hours. We can assume that first- and second-graders need around 11 hours. If their school begins at 7:10, we can safely say they have to rise no later than around 6 a.m. and go to sleep around 7 p.m. On Aug. 11, 2025, the first day of school in Escambia County, sunrise is at 6:13 a.m. and sunset at 7:34 p.m. Then as the days get shorter, sunset becomes earlier. To get sufficient sleep, the youngest children would have to go to bed before sunset and get up before sunrise. Put all the research aside. Common sense tells me that those times are unreasonable and that the majority of children will have insufficient opportunity to get enough sleep.