The proper thing for these parents to do is organize, arm themselves, head down to the school administration buildings, and kill every official, employee, and agent in sight. If the school board members are not there, hunt them down, and kill them too.
No doubt, that would result it an armed SWAT response, arrests, and deaths.
It would not be legal.
But, it would be proper, and therefore should be legal. Specifically, it should be an affirmative defense against the charge of murder that the slain (a) be an (1) elected member of government, (2) employee or (3) other agent thereof; and (b) (1) had committed, (2) passed into law, or (3) supported the passage into law of (c) an unconstitutional measure that (d) was (1) applied, or (2) applicable, to the accused. In this case, the students', and by extention their parents' fourth amendment rights were violated.
Governments are supposed to exist at the pleasure of the people and be their servant, not the other way around.
The founding fathers didn't go far enough with the second amendment. They had the right idea, that in extremis, armed rebellion against a tyrannical state was justified. But, they failed in thinking a separation of powers and enumerated restrictions on government powers, would be sufficient to ward off that necessity. So, now we are left with a society that has no idea when to take up arms against the state, save the vague notion of "when enough others do". And so, we just sit and look at one another. When the time comes (and, it will), the response will not be a gentle local reminder of who's the boss, but rather a widespread revolution that runs a clear danger of leaving a power vacuum, as revolutions tend to do.
It would have been far better for there to be a "rulebook" as it were, that clearly enumerates, but not in an exhaustive sense, when to kill an agent of the state.
Government is best viewed as a beast of burden: useful for a time, but to be put down when it has outlived it's usefulness, or otherwise become ornery.
Trust no agent of the state who is not willing to enumerate a number of actions that, if they undertook, would justify their killing under the affirmative defense of protecting constitutional rights.
Radical? Obviously, I don't think so. Affirmative defenses are not legal "walks in the park". They shift the burden from the state having to prove guilt beyond a reasonable doubt to the accused having to prove innocence under the specific affirmative defense shield, having admitted to comitting the act under consideration.