How would you go about getting a schoolboard member off the board?

Answer 1

you have to find out the specific rules in your jurisdiction. some states/counties have recall elections, others don't. some have impeachment.

you could also call local newspapers and talk to the reporter covering the school board. Then, you give them the information you have about why this person should be off the board. If lots of people agree with you, or just a few right now, you hold some kind of event and invite the reporter to that, so that you can make your statement about this board member.

if enough people get upset about a good enough reason, the boardmember might resign.

A first step should be for you to contact that schoolboard member about your concerns and listen - actually listen - to their response.

Answer 2

You could either wait until the next election, or attempt to get a referendum passed to get them off. Either way, good luck.