Our school system uses Math in Focus and I have particularly impressed with the enrichment packets. You might also want to see what your school district uses so your child does not have to do the same work twice. When DD was that age, I just used these super skinny and inexpensive workbooks called Flash skills. She could get through one in about a week and when she was 4 or 5, she covered the entire first grade curriculum in about a month (at only 10 min a night).