With classes set to resume later this month, finding time for sufficient sleep will become a challenge for your school-age child.

Fewer than 1 in 5 middle and high schools in the U.S. began the school day at the recommended 8:30 a.m. start time or later during the 2011-2012 school year, according to data published this week by the Centers for Disease Control and Prevention (CDC).

To compile those findings, the CDC and U.S. Department of Education reviewed start-time data from nearly 40,000 public schools.

Key findings:

In 42 states, 75-100 percent of the schools started before 8:30 a.m.
The average start time was 8:03 a.m.
No schools in Hawaii, Mississippi, and Wyoming started at 8:30 a.m. or later.
Louisiana had the earliest average school start time (7:40 a.m.), while Alaska had the latest (8:33 a.m.).
Researchers have found that insufficient sleep is associated with several health risks and poor academic performance.

In 2014, the American Academy of Pediatrics issued a policy statement urging middle and high schools to modify start times to no earlier than 8:30 a.m.

The CDC said parents can help children practice good sleep habits. For example, a consistent bedtime and rise time, including on weekends, is recommended for everyone, including children, adolescents, and adults.

To learn about CDC’s efforts to promote sufficient sleep, visit http://www.cdc.gov/sleep/index.html.