If your children are totally unvaccinated, they shouldn’t be around many people at all. They could be exposed to measles, mumps, flu, cold all the time. They may have been in a protected environment in high school if all the other students and staff were vaccined, but covid is new and we don’t even know if vaccinated people can spread it.
Even if a school doesn’t require students and staff to be vaccinated, huge numbers from those schools may opt to be vaccinated anyway. I’ll bet that some of the smaller LAC will have close to 100% compliance - voluntarily. It was just 3-4 months ago that students were driving across state lines to stand in long line to get vaccines, schools were volunteering to be vaccination sites, that students were desperate to get vaccinations so they could go on spring break.
Your children could pick a school where everyone wants the vaccine, even if not required.