For first grade math, we continued with Math Mammoth. I switched at the end of Kindergarten after a semi disastrous math year with Saxon. Saxon, though a great program was not a great fit for E. She was not grasping concepts and was simply memorizing "tricks." In the end I was discouraged that we had spend such a focus on math in kindergarten (45 minutes to an hour a day) to yield so little. And I hated spending 15 minutes introducing a concept only to have 1 or 2 practice problems or none on the worksheet. So we switched and I have been thrilled!
At first I was nervous to leave the "scripting" of Saxon to something I had a hard time even picking out the "teaching." As time went on that became the best part! Math Mammoth teaches concepts in such a way you barely notice you are moving to a new concept. I love how each step in the "worktext" takes you just a little farther into the topic. MM is based on the Asian system of doing math like Singapore math, but unlike Singapore has more practice and does not possess the "conceptual leaps" some complain about in Singapore. E is not necessarily "mathy" and I thought Singapore would have been a stretch for her, but MM gives the Singapore edge in a way she can understand. I also love that it is written in a way that it is often able to be done semi independently. We do add manipulatives occasionally, especially when introducing a new or challenging concept.
Math Mammoth is a complete curriculum and does not need to be supplemented, however, we found that while we liked the mastery of MM, E needs a little more spiral for review. So this year we added in Right Start Games. They have been the hit of math this year! They are a perfect companion to MM and add just the right fun spiral review E needed. E says she doesn't "like" math, but she loves to play math games!
Another huge plus is the cost. Twice a year Homeschool Buyers Coop has MM on sale and sell the download of grades 1-6 for up to half off. I got 6 grades of math for around $65! (Just a note if you print in color as I do the savings quickly diminishes, but hey!) Math is one area I didn't even consider looking at other curriculum for next year. If it's not broken, don't fix it!