ooooh, yes :-) I think it's just a language issue, isn't it? He means "easy to concentrate on/hard to concentrate on"; you mean "unchallenging/challenging". The situation seems natural enough - I think you just need to do some terminological clarification!

I would definitely mention it to the teacher, in the context of saying something positive about the enrichment and saying that your DS has made a comment about how much easier he finds it to focus on this work, and isn't that interesting?

Email: my username, followed by 2, at google's mail