I'm in MoCo and just heard from a teacher friend who explained a little bit. It sounds like they are shifting to more tiers of start times so that fewer busses are needed.
This is what MoCo already does:
HS 7:45a-2:30p
MS 8:15a-3:00p
ES1 9:00a-3:25p
ES2 9:25a-3:50p
Here's an article from today (9/13)
https://www.wbaltv.com/article/howard-county-public-schools-new-start-times/45126415#
It looks like they are spreading times to split apart Tier 2 MS and Tier 2 ES.