[Know your rights]

"This is cocaine", he said. He glances over to see the janitor listening in. "Just kidding, guys", he adds.

Pure speculation ... and in any case it was not in fact cocaine.

The janitor is expected to keep quiet about this?

Red herring. The authorities are expected to not assume that jokes are meant seriously.

[robertpaulsen]

"Pure speculation"

Ah. You know exactly how this went down, huh? My description is just as likely, maybe more so, since it explains why the janitor reported it.

You can't explain it except to say the janitor shouldn't have believed the kid when the kid claimed it was cocaine, but he should have believed him when he said he was kidding.

Uh-huh.

"and in any case it was not in fact cocaine."

Neither the school nor the police said it was. If it was cocaine, he would have been charged differently.

He was charged with possessing a substance that looked like cocaine and was represented as cocaine to his friends. That is a Class 3 felony in Illinois. That is also against school policy.

The state and the school couldn't care less what the substance actually was.