I started home schooling my D in second grade, we started with level 1 in Singapore, just to solidify the style of math they encourage. We completed 1A and 1B in four months. We skipped where needed and lingered when necesary. I don't regret stating at the beginning. That being said, there is review in level 2, but the basic concepts of mental math, grouping, and word problem constructs are expected to be known. Sorry, don't think I'm helping much. I guess you just need to decide how much time you want to spend on it. Good luck.