School board members are elected by those within the school district. How long they serve depends on local rules. (It's usually a 2 or 3 year term.) In most communities, anyone who is a resident of the district, a registered voter, and 18 or over can run for school board. Most school board elections don't have big turnouts, and so it's very possible for conservative candidates to get elected and make a substantial difference to how local schools are run. In some cities, conservatives have gotten together and formed slates, so that a whole group of conservatives gets elected at one time.