S-T,
If I understand you correctly, your ds8 completed the pre-algebra initial assessment with 100% mastery and you are wondering which level would be best to go to next. Is that right? What a smart kid!
Do you home-school? What is the highest level your child has been introduced to at home or school? Does he study math independently?
If he doesn�t mind, I�d just have him take each higher assessment until he scores below the 90% and has something to learn.
Also, our state (IL) supposedly has the lowest math standards while MA and CA have the highest, so I selected MA state standards on ALEKS for my kids and CA standards for my nephew to ensure they learn everything available for any given level.
