It’s buses. Unlike most other states, in Massachusetts the individual school districts bear the full cost of school buses (and manage their own vendor contracts), so districts stagger the school start times so the same buses can do multiple pickups and drop offs.

Look at the very big difference we have between high school and elementary school start times. At least some districts that tried to change start times in the last few years have run into huge problems with buses. As is often the case with buses in Massachusetts, it’s not even how fast the bus can complete the route, it’s how fast it can get back to the start of the route to do it again.

When I grew up in New Jersey, my school bus to middle and high school was a regular public bus with a school voucher that ran its route all day. It started in New York City and ended 100 miles away. My town didn’t pay for the same bus to come to my street to pick me up then come by again to pick up my younger siblings.

But Massachusetts has a lot of densely populated areas with no state bus service and the major road routes that aren’t highways are old and chaotic. The bus drives out from the depot to the school district and runs its routes within the district.