Abundant research indicates that achieving high-quality, consistent sleep is one of the better things we can do for our health. It helps prevent sickness and chronic disease, it helps us avoid accidents and improves our mood. Good sleep hygiene even ups our overall life expectancy.
Despite all this evidence, many adults in the modern world are relatively sleep-deprived: an estimated third of all US adults report getting less than 7 hours of sleep each night, and about 20% of US adults report feeling sleepy most days.
Some of this sleep deprivation is the consequence of health or environmental issues, like sleep apnea, insomnia, or environmental noise from nearby traffic. Others get poor sleep because of unhealthy habits, like choosing to stay up late, drinking, taking sleep-impacting drugs, or eating before going to bed.
It’s estimated that about a fifth of the US adult population gets less than five hours of sleep per night, and this can lead to even more serious sleep-related health issues, alongside higher instances of dangerous behaviors, like falling asleep at the wheel (about one in 20 US adults reported having done so within the past month in a 2009 analysis).
These trends are more or less population-wide, though children are less likely to be sleep-deprived than adults, and older adults are more likely to have trouble staying asleep than middle-aged and young adults.
Teenagers seem to have fewer biological issues with sleep, on average, more easily falling and remaining asleep, but many modern societies have structures that make attaining regular sleep schedules difficult for them, too.
In the US, for instance, many middle and high schools start so early that students aren’t able to get a full night’s rest.
Young people are more likely, on average, to be night owls—to have circadian rhythms that keep them up late and cause them to sleep later into the morning. Those rhythms change, on average, as we get older, till most of us hit the hay and rise early in middle-age and later. But when we’re in our teens, the majority of us are driven by our bodies and brains to stay up late and then stay in bed late, too.
Most US schools, however, start between 7:30–8:00am, and some begin even earlier than that. This can be beneficial in that it allows adults, like these students’ parents, to get out the door and to work on time after helping their kid get out the door and to school, but it’s less beneficial, according to a bunch of studies, for the students.
In particular, it seems to dramatically impact their level of wakefulness and psychological well-being, and consequently, their academic performance.
A recent working paper published in May of 2026 looked at the impact of California’s Senate Bill 328, which mandated later school start times throughout the state, on adolescent sleep habits, mental health, and academic outcomes.
The researchers behind this paper found that the share of students sleeping at least 8 hours per night increased by 13%. They also noted that boys saw significant reductions in sadness, hopelessness, and suicidal ideation, while Hispanic students saw large reductions in difficulties with concentration throughout the day.
Throughout the state, Math and English scores in 8th grade improved by about 0.08 to 0.10 standard deviations, with the state’s most disadvantaged students seeing the largest gains. They also saw a decline in high school dropout rates.
None of which is the final word on this matter, as this is just a working paper, using public data in one state, which implemented one relatively small tweak to school starting times.
That said, it does suggest that even minor adjustments to school starting times might bear positive fruit on student outcomes and psychological well-being.