Empty school buses have been steadily increasing their use of Decatur St, entering from Brookline. That can only lead to a left turn onto Pearl from Decatur.
1. The turn onto Decatur from Brookline, and onto Pearl from Decatur is too narrow for these vehicles to navigate. They often block traffic while they wait for other vehicles - already there - to move. And they often "play chicken" forcing other vehicles - which were already over 1/2-way down Decatur - to back up the length of Decatur St and let the bus go by.
2. It's not clear what school is being serviced by these buses. From Pearl, they could get to the Morse School on Granite St - but if so, why were they headed down Brookline in the first place. They could also have been heading to the Amigos School on Upton - but again why are they coming down Brookline when they should be taking Pearl over to Magazine or Pleasant?
This happens in the morning during rush hour as well as during mid-afternoon. Bus #115 is a regular, but I'll post the numbers of others as I see them.