Parents in Montgomery County have started a movement to start high school classes later, pointing to research linking extra sleep to the healthy development of teens.

As of Wednesday afternoon, an online petition to move the first bell back from 7:25 a.m. to 8:15 a.m. or later had gathered 2,350 signatures, virtually all from county residents. Mandi Mader, the mother of a sophomore at Walter Johnson High and a sixth-grader at Tilden Middle, created the petition as the first act of the Montgomery County chapter of national advocacy group Start School Later.