For the student: You can’t grow crystals on your screw overnight.
For the teacher: You can’t let them do their project at home and you should not take their word when they say, “yes, the crystals are growing.”
I suspect it was a bit humiliating to display that plain screw in a jar of brownish liquid in the gym, there for all the world to see. We are told our students must never be humiliated. But I am betting “Elliot” learned something from having to display his screw. Next time, he may be more honest and he may try harder. I wasn’t mean about it. I just looked at the screw, then looked at the boy, who had the decency to blush.