Home schooling is not economically feasible for a lot of people. Private school is also not economically feasible for a lot of people. If the sniper mentioned a threat in the note about children it would make sense that the schools would have to shut down. If they received a threat and they kept the schools open, and a kid got shot .. well you know .. the school system would have been negligent and everyone on this post would be slamming the schools for not shutting down.
If this causes more people to home school and educate their children themselves and become less dependent on an over regulating, over burdonsome government ... that is good.
IMHO, we NEED vouchers or some other program to give parents the choice that is (again, IMHO) inately theirs in the education of their own children in this nation ... for exactly the reasons you gave.