I have 25 students in my introductory creative writing class at Texas A&M University, College Station. I can't speak to the class sizes at the other A&M system universities. It would be a good thing to survey.
At the other universities I have taught creative writing--UT/Austin, UT/Tyler, and UT/El Paso, the class sizes were kept to 15.
What a world of difference it makes in the way you can help students with their work and relate to them as human beings.
If you are looking for a creative writing job, be sure to inquire on the size of the intro creative writing classes you will be teaching.