How on earth did the friend get a copy of one of the pics? That's disgusting if she's participating in sharing the photos around.
Honestly, if I found out that my child's teacher took cocaine and other drugs I would be very concerned. But that's one of the reasons teacher's personal lives should not be gossip fodder and shared around the parent body. Because when people know they're bound to have an opinion on it and no good will come of that. Their private lives should stay private and I don't want to know. I really don't. Its not something I can control, and its not my business, and no good can come of delving into personal lives like this.
If someone tried to tell me inappropriate things about a teacher at our school I'd stick my fingers in my ears and go la-la-la. I want to stick with blissful ignorance thanks.
And more seriously, I'd tell them to pull their head in and stop spreading gossip. It taints the person spreading it as well as the person being gossiped about.