I have used Singapore with my oldest two (6th, 8th) and youngers (I have 7.), and will continue to use it with the youngers. We have combined with MUS in the younger grades, but I am considering not even doing that. My plan for the youngers is to use a pre-algebra program in 7th. My older two did MUS pre-algebra after 6A and B. No problems here. Singapore math has really taught my students how to think mathematically, not just fill in the blanks.