That’s the way it’s done in our school. It works, kinda. But illegal stuff still gets in occasionally. And here’s how. Student A goes through the security process. He’s clean.
Then Student A goes to a remote part of the building - maybe a restroom - and opens a window. Student B - who is waiting outside - throws the contraband through the open window.
Sometimes Student B isn’t even needed. Student A will leave the contraband on the window sill the night before.
I guess this method could be thwarted by stationing teachers outside on all sides of the building, all day long.
YOUR Scenario is why COCW should be allowed in EVERY school/classroom
There will always be ways to thwart the process, but if thyey are tken care of right away you can fix them. Like maybe keep all first floor windows closed. or some other solution (check window sills at end of day)