I have choosen not to skip levels and very glad that I made that decision.This past year and half, my DD finished TT5,TT6 and TT7. I had thought about skipping TT7 and am very glad that we didn't. TT7 problems are more difficult than TT6 include factoring fraction and has a geometry unit. I think it would have been to much of a jump from TT5 to TT7. We own Pre-Alg and Alg I . And I think it would be to much of a jump to go from TT7 to Alg. I We are going to start Pre-Alg. this fall. I would rather have a child move quickly through material that came easy and be able to slow down on math strands that are not secure. Plus TT has a great resale valve.
Hope this helps you,
plaa