Here in York, Pennsylvania I see this more and more, you know they are going to stop soon but how soon remains the question, sometimes I think the bus drivers are deliberately doing this mess up the flow of traffic because nobody will pass them with the strobes flashing even if it legal.
They’re supposed to be using the yellow flashers as they come up on the stop. They’re trained to do it that way, or at least we were. It wakes up any distracted drivers before the red ones come on (you’d be surprised how often that happens early in the morning, especially for the really early runs). I forget the exact distance we were told, but it varied depending on the road and the location of the stop. It’s not so much for the drivers behind the bus, but mainly to gain the attention of any drivers coming the other way, who haven’t been behind the bus the whole way and therefore aren’t thinking “school bus”.