I assume you're talking about military recruitment. And I'm betting that the government's position is that the US military is allowed to recruit in publicly funded buildings including schools.
I remember seeing those recruitment tables set up once in a while when I was a student many years ago. Usually it was the kids I would expect talking to the recruiters.
There's a pragmatist in me that thinks maybe it's okay. Lots of kids have no direction, aren't suited for college, etc... Then there's the fact that voluntary service is part of what makes us strong as a nation.
But then I think that these kids can't even buy cigarettes yet. They're considered too young to buy a lottery scratch ticket. But starting to make decisions on whether they want to go to war is somehow OK? Yeah, that bothers me. I think I would say that we shouldn't allow recruitment of minors - which would prohibit going to high schools.