If a teacher somewhere here in Europe would allow himself to seize private property, it would be a scandal and the teacher will most likely loose his job - rightly so. If it isn't like that in USA - then I am, frankly, shocked that a country which is supposed to be build on democracy is permitting such crude violation agains the basic constitutional order.
There are things like laws and basic rights (one of which is private property ownership). The school should not and can not "enforce school rules" by committing crime such as illegal property seizure. If using a laptop is agains the rules: you put the child out of the class and call his/her parents. If the child is playing with his phone during his exam, you fail him and call his/her parents. This is how the things should be done in a democratic, law-governed order.
To make things clear: the only cases when the property can be seized are: a) the property caries a clear and immediate danger (weapon, etc.), b) the property is not legal (drugs, alkohol in hands of a minor etc.), c) there is a court order permitting the seizure. Confiscation of a laptop is illegal and a criminal act under ANY law known to me. Sadly, people still insist on that "teachers can take stuff" thing, which is nothing more then a relic from old european teaching system. Interestingly enough, Europe has long moved ahead, yet judging from responses in this thread the USA still seem to miss the times of parental despotism.