Google "York, PA" and you'll see that school boards can indeed "promote" a political agenda --- by "banning" certain books from history curriculum if they cover racism or slavery, and removing books from libraries. Or fighting State Health Dept. mask mandates.
Look far enough into York County's history, and you'll see the York County Dover School District wanted to teach Creationism, until the SCOTUS weighed in. That's still a touchy subject in these parts.