Effective protection involves hardening the target, it is why the President's kids go to a school with armed guards. That school always has armed guards regardless of whether the man in the White House has children or not, this is because the kids are targets.
The President's children are protected effectively, while our kids get a "no gun zone" sign and are targets for anybody who wants to kill many people and cause the most emotional harm with impunity, until the cops finally arrive much later than they were needed.
If I was one of these parents I would be suing the school district. If I were in the theater in Aurora I'd be suing that theater. Any place that puts up a no gun zone sign is, IMO, taking on 100% of the responsibility for unprotected targets and absolutely should hire some protection for those they have ensured would become targets. When seconds count the cops are minutes away, and Columbine has proved that there is no guarantee that when they get there they will be effective at all.