My ex-wife is a teacher. My oldest daughter from my second marriage is a teacher, and she's as right wing as anyone I know. An interesting contrast to the bulk of the teachers she works with in our local high school.
As for your teacher, simply state the facts. Tell him how impressed you are with his liberal arts degree...

Remind him that those who can, do. Those that can't do, teach. Those that can't teach, teach gym and those who cannot teach gym are promoted to administrators.
Remind him also that the hiarchy of a typical school district is similar to a cesspool, inasmuch as the big turds seem to rise to the top. Tell him you expect that he will live up to his destiny and achieve a leadership position within the rarified world of public educators.
Oh, and the next time some pompous teacher suggests that joining the Navy is the easy way out, remind him that the easy way out is to avoid serving. Tell him that responsibility to something beyond his own interests builds character, as does discipline. Remind him that self-righteous windbags living on the public tit is, without doubt, a waste of taxpayer money.
My regards,
Widewing