As long as the kids are still only getting calculation and haven't been allowed to dig into concepts (beyond the basics of sets and arrays and that sort of number concept stuff that kids do get in 1st or second grade), I really haven't seen much deeper you can go. (And I've been looking!) A little deeper than just a page of problems, sure, and every little bit helps. I am certainly a firm believer that problem solving is the way to approach pretty much *ALL* math. Word problems and tricky thought experiments are GREAT! But I'm not sure I believe that you *can* effectively go a whole lot deeper than the norm in early math without going pretty far from the normal ways to teach math. Calculation is calculation is calculation...
I agree, Kriston. In the first few years there is really not too much you can do but to move ahead. Now with DS5 doing 4th grade math we finally got to the point where we can go deeper and do problems which he finds challenging while having the math skills needed to figure them out. I am really exciting about that part.
