Yes to sirfred's point. Examine how you feel about school, maybe he is saying this because he knows it will put him 'on the same side' as you. Him saying that might give you, subconsciously, the satisfaction of being confirmed in what you expected; and kids do pick up on that kind of thing.
DS' teacher once pulled DP up 'for a word' and it emerged that DS had said to her that 'Daddy says I don't learn anything at school' 
Whereas DS does (of course) learn at school, it is true that we (DP and I) tend to think that school is fairly inefficient for learning, and that it is quicker and more efficient to learn things 'at home'/one-to-one/in context/out of self-interest... and that therefore DS on balance probably learns more out of school than at school. And we do think badly when schools (in general, not our specific school) focus more on assessing than on teaching (e.g. spellings or times tables - children to learn them by themselves/at home, whilst school merely tests them).
But whereas it is true that we think these things, we do not believe that school is negative, we continue to send DS despite HE being an option for us. We have a well reflected stance towards school, not blindly positive, nor predominantly critical, but seeing the downsides in context of the whole.
We realised then that we have to be more careful about how we express our own feelings regarding school. Not to deny that we feel this way, but to be a bit more nuanced about it, so that DS doesn't get the wrong end of the stick and starts to believe we feel that school is 'a waste of time'.
Also what other PPs have said: DS enjoys school for the sake of his friends. These days (now in Y3) if he said that school is a waste of his time, he would mean that he isn't getting enough time to do stuff with his friends. Obviously break times and free play are now fairly limited, but in turn a lot of the actual school work involves being with/working with his friends, which is fine in his perspective. What he finds boring/time wasting is doing (too easy) worksheets individually. Fair enough, IMO.
But then, DS lives for social connections, and 'learning' is merely a side effect/means to the end. It would be different, I suppose, if he were primarily motivated by learning.