What is the plural of the abbreviation for Teacher Assistant?

Answer 1

If my grammatic rules sever me correctly, the plural of "Teacher Assistant" is:

Teachers' Assistant

If the apostrophe appears before the "s", it denotes assistance to one teacher. When the apostrophe appears after the "s", it denotes assistance to many teachers.

A hillbilly illustration may be educational here.

ya'll = directed toward a gathering of individuals

all ya'll = directed toward a gathering of families