I agree that in general, classrooms shouldn't be a place to push a particular political ideology or campaign. However, simply being gay in school isn't a political campaign. It's a recognition that a teacher's classroom is a safe place for gay kids. If that's political to you, even if the teacher never once mentions a political candidate, you've probably got a problem with the existence of the gay kids.
The governing body of the largest Mennonite denomination in the United States passed a resolution on Sunday (May 29) confessing to “committing violence against LGBTQ people” and committing to LGBTQ inclusion.