Actually you can make it work with baseball and softball playing in 2 different division if you wanted to. Although the teams usually play on the same day at different schools, they don't use the same field and the bus trip is the same if baseball is traveling and softball is at home or vice versa.
Hollis-Brookline has boys s****r still in D2 and the girls s****r team moved up to D1.
Baseball could move independent of softball if the school wanted to put in the time to make it work.