Hi Helen, You just need to insert one comma after classes and 'to be' after find and it should be good. For example: "Kids could take moderate after-school classes, which they find to be fun."

Actually, it depends on what you are trying to say. If you mean that children naturally enjoy this type of class, then you say "Kids could take after-school classes, which they find to be fun." But if you mean that the children might not find this type of class fun unless you pick it carefully, then you should say: "Kids could take after-school classes that they find to be fun."

I agree with Albert, about the comma. But I must say that the words 'moderate' and children's classes seem to be a strange combination. I am not sure what the sentence is about, but you might want to ensure that it is the correct adjective.