I didn't say he forgot. Said he slipped up. Here's a recent article with more details.
"I explained to my principal that I couldn't in good conscience pronounce masculine pronouns to refer to a girl,” French teacher Peter Vlaming says.
www.dailysignal.com
The quote below lets you know he wasn't just in there saying she/her, but instead was just always using her name.
"The ultimatum said that in order for me to be allowed back in the classroom, that I would have to proactively use male pronouns, in any instance, if they suspected that I was using the name instead of he or him or his, that it will be grounds for my termination."