While I do agree he should have mentioned the difference in layers, you should not forget that they're 11-year old kids. Even I had to struggle to understand the difference between L1 and L2, let alone students who don't even care as I do. Whoever does, can find out what's true and what's not by themselves.

Now, as for the following, I very much disagree;
The Lightning Network is innovative (& cool). A decentralized system that's adopted globally can't scale seriously. While changes in the block size can satisfy the users to some extern, it's just a temporary solution. People must have a ledger of their own, unless we want bitcoin to remain a non-recognized, alternative payment method. Period.

I'm convinced half have understood why mining is necessary, from the bitcoin dot org video. Now as for the LN, again you can't expect them to fully understand it. They don't even know how to solve a quadratic equation yet. Honestly, I'd do the same if I was a teacher.

And what did you want him to do, smarty-pants? What if they formed a biased opinion about the 10-minute interval and in their later life, got attracted by some shitcoin that's faster? Again, he taught as he should.

So would it be better if he didn't make this lesson at all? Get serious. It must have been an awesome time for those 2-3 who will get involved in the future.