Limited number of buses are staggered for HS/MS/ES. Starting all schools at the same time would cost more in busing. (Reordering is a partial solution.)

HS students/parents want students out of school in time for after-school jobs and activities.

Well there are multiple very sensible reasons to do it. (Whether those reasons actually outweigh the negatives is a different story though lol).

Given how far east Massachusetts is in the timezone, the sun rises and sets earlier here than most other parts of the country. Having enough sunlight in the morning is important to ensure kids can get to bus stops or walk to school safely. Older kids can navigate more safely with less light so they are sent in earlier. Having enough sunlight after school is also important for safe travel home and so kids can have more time to participate in after school activities that require daylight such as sports.

I think most people (at least in my experience) acknowledge its better for teens to start school later but they are unsure of how to fix the sunlight related safety issues. Installing more streetlights and lights around sports fields would be a solution but most towns don't have the money for that.

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.