> what related content would they advertise? Guns? Back to school supplies? Without knowing why a person is on a page, it's difficult to understand what related products might appeal to them.

Training for teachers? Security services? Access control systems? Yes, a lot of those reading are parents, not teachers, but what do you think they'll do if they are convinced something exists that will reduce the risk of school shootings?

Editing: ad "targeting" as it has existed so far has also been insultingly, embarrassingly bad IMO. Even Google tried for years to send me ads for Russian, Ukrainian, Philippine and Thai dating sites. Round robin. I was delighted when they started showing me Wordpress ads.

Those are not relevant either but now we are approaching something useful and not actively insulting (I'm very happily married and have small kids.)