I'm struggling to find a good resource on the internet. I have two girls. The past few weeks, I told myself they had forgotten over the summer, they'll catch up if you review stuff with them enough. After speaking to former teachers who are also worried they're still behind, I'm getting concerned. They can't do basic arithmetic (2 + 2), struggle to use manipulatives to solve, and putting numbers in order is beyond them. This is 2nd grade.