DS12 is in 6th grade in a charter school and I was wondering if there is a way to assess his level so that we can determine where to start in the MCT ? He has always done well in English/Language Arts but I do not think his ability to write is that great and have similar concerns about grammar/vocabulary.
The Magic Lens Series might be a good place to start. You could also try some Caesar's to get an idea of how it flows. Caesar's might be to easy but it gives you a good foundation for the rest of the series. It can be as rigorous as you want it to be.
