District high schools will have a new start time of 9 a.m. starting next school year.
The district made the announcement in a letter to staff, shared with Action News, on Thursday morning.
"Research shows that later start times for high school students enable them to arrive at school more alert and ready to learn. In addition, since a majority of our high schoolers are responsible for making their own way to school, later start times promote safe travel in the mornings and afternoon," the district said.
The 9 a.m. start time covers all district high schools including those with middle grades.
There are four high schools that are excluded from the time change because their schedules must align with partner institutions, the district said.
Pre-Kindergarten programs that are located in high schools are not affected and will maintain their current schedules.
Elementary schools in the district, defined as schools serving Pre-K and 8th grade, will also keep their current bell schedules.
"We recognize that changing start and end times can present challenges to families, and remain committed to providing support to families wherever possible," the district said.
The Philadelphia teachers union says the schedule change goes against the contractually outlined procedures, and that they have shared their opposition with the district.
The district has been working to standardize daily start and end times at its schools in an effort to reduce the amount of time students spend on buses, help ensure buses are on time more often and allow for consistent cleaning of high-touch areas on buses between runs.
The district has been in the process of aligning schools to a three-tier bus schedule amid the national bus driver shortage.
Upper Darby School District officials say they are seeing success after shifting their start time to 9:45 a.m. while also implementing three ways for students to learn: asynchronous - from wherever they'd like at whatever time they'd like, synchronous - where students remote live into class at it's scheduled time, and traditional in-person learning.