We have participated in a couple of Noetic Maath Contests, and my kids love it! It's flexible. We can register online by ourselves, without the need to find a hosting center, though we're considering looking for one to make the experience feel even more official for the kids. Despite this, my kids still received good-looking medals, which really made them feel good– and at the end of the day, that's what matters. We just recently enrolled in Challenge Math Online. It seems to strike the right balance with weekly practice that keeps them engaged without being too overwhelming. They seems to enjoy doing it, which was a pleasant surprise/