What sorts of public campaigns have you witnessed for school boards where these sorts of asinine discussions are raised? This would be injected into the meeting agenda as a minor item lumped with a bunch of others which would have all been approved with a single quick vote so they could move on to much more important topics such as wasting money on some frivolous sporting event or booster club meeting.
These sorts of discussions only come up during campaigns AFTER they've been put into place and one person in the community stands up to say WTF and is ignored at meeting after meeting by the administration who put it into place with the consent of the morons on the school board and then runs solely on the platform of removing this one item.
After they spend $1500 running, get on the board and abolish the decision, something else comes up which is possibly worse and they are powerless and clueless to stop it.
This is the problem with all local level government bodies (city, county, etc). People run on a single stupid platform, are elected, and stay there forever or are booted out because someone else has another single stupid platform of the day.
Most everyone else just shrugs, says ok, and their kids get scanned.
(As an aside, my kid is NEVER, EVER, EVER, EVER getting their fucking eyes or fingerprints or any other biometric data scanned for school -- fuck that noise).