I think I might enjoy the CPS scenario... let them call CPS, and wait for CPS to arrive, and then discuss with CPS who is endangering the child, the parent or the school. I'm pretty sure a judge will quickly decide whether their rule makes sense or not, and I think judges in child protection cases are going to quickly side with what's important for the child.
I HATE this kind of nonsense, and threatening you as a parent is only making things worse. Why not offer a way to handle this on a simple website? It would have lower cost to the school and be more accessible to anyone with any device able to access websites. Nonsense.
Well the judge will likely rule the app is bullshit, but in the meantime CPS will argue they need to go into your house, look to see if you have a dirty dish, or the wrong proportion of snacks to vegetables, or maybe take notice your child is playing independently outside while they come around. Then they will portray that in the most insane way possible, and since it is a civil and not criminal process their is no requirement anything is shown beyond a reasonable doubt.
There's also the problem that once they have your kid, the tables are completely turned, rather than them showing why they should take them, now you have to show why you should get them back and that is a process that can be dragged out for over a year.
Unfortunately CPS has wide latitude, secret courts, and the ability to unendingly fuck with you, so it's better just to not "invite" them in your life if you can. And if they do manage to snatch your kid, note they give so little fucks for the kid that their contractors will leave a kid in a hot car to die because apparently that's safer than being with their parents.[]
[] https://abcnews.go.com/US/3-year-dies-hot-car-custody-contra...
Spoken as a non-parent? No parent I know would be willing to test fate in that manner.