I've even seen this in the wild used just for session (as in practice session or lesson). It's really just a period of time.
Note there is a sentence in this skill Mwalimu atakuja kipindi cha tatu. If I had to wait that long into the school year for a teacher, I'd be rather unimpressed. So I'm pretty sure kipindi can be used like the English "first/second/etc period" of the school day.