BMS

Stands for Bedford Middle School, a middle school in Connecticut with a bear mascot.

Or an acronym for "Beating My Son"

"Hey man, you going to BMS next year?"
Or
"Hey man, I'll be there in a sec. I busy with BMS."

B.M.S.

Stands for Bedford Middle School, a School in Connecticut, and may have been referenced in the show "American Housewife"

Or

An acronym for "Beating/Beat My Son"

"Hey man, I'm going to B.M.S!"
"Sorry gotta cancel, B.M.S."
Etc.