Unless there was a public record of any work sanction, such as an arbitration that went against Joe, no employer would be stupid enough, especially the school board, to divulge confidential employment records. It's this pesky thing called "privacy" afforded to us by both federal and provincial privacy laws. If it were a work colleague, then it would be merely hearsay.
As for criminal records, I'd be surprised if joe has one. The boards do criminal checks on parents who want to volunteer it's hard to imagine they wouldn't do checks on teachers especially.
As per usual, Druggie is speaking out of the oriface that is his anus.
I think Druggie would be wise to shut it because he is liable for libel and slander. JMHO