I am going to go against the majority here and say, I don't think 11 is too young, if schools should be doing protective sex ed at all.
Eleven is the average age for children to be exposed to pornography, which is horrible, but it's not really on the schools I don't think. It's mostly due to access to the internet. And some of what they can see is really horrible.
As for the definitions of hard and soft core, the latter doesn't show actual insertion and often not penises at all, often the people are only pretending to have sex. Arguable some mainstream television shows these days include it. I'm not sure that it's terribly useful to young people to know this, but it could be put pretty simply as saying one shows real sex and one doesn't, but both are pornography (and problematic therefore.)
I'd kind have expected the lesson to tell the kids that though, there's no point asking the children - how would they know? It would be a bad approach in any subject to ask kids things they don't know the answer to. I wonder a bit if it's a problem with the way it's been adapted to send home?
Why they would talk about specific flavours of porn I have no idea, I can't see any value.