That's completely impractical. There are cases in which police have interviewed and/or searched the cars & dwellings of more suspects than there are policemen in the force.
Cops are human. They can and do make mistakes.
Yah. The issue isn't that the cops got involved, and asked some questions. The issue is that once they *knew* it wasn't a bomb (or they'd have called the bomb squad), they doubled-down and continued, rather than just go, "Guys, the kid make a *clock*. Really, Principle Mushhead, you called me in for a *clock*?"
The ACLU is aware of the case. I hope the school and cops will wise up, offer an apology, and let it go.
Meanwhile, that distant sound you heard was of a budding engineer having his soul squashed.