Private school with a very gun friendly administration. Don't laugh. I know some public schools have facilities to host classes if you ask...and you may have to press. They are public schools and public buildings. They would most likely charge a nominal cleaning or utilities fee. In the long run it may be more a hassle than it is worth unless you know the attitude of the principal or superintendent.
Our public libraries have meeting rooms. They charge $25.
Your congregation may let you hold one at the building. We put about 70 folks through several classes at our congregation.
Community centers, VFW halls, meeting rooms in fitness centers, restaurants, hotels ($$), senior citizen centers, Boys Club, YMCA, community centers, businesses with meeting rooms, get creative, it never hurts to ask.