The actual grade level is irrelevant in my opinion, since each kid has a different level of maturity.
The pace is very fast. There are three categories of assignments -- regular, challenge and web-based Alcumus problems. So it is up to each kid as of how high he/she is willing to reach, and how much time you have. The challenge problem sets are difficult, and the writing-up can take a lot of time, especially for younger kids, but they are the most rewarding part of the class. The book is very readable, with a lot of exercises, but it is a very thick book.
So, the materials are very good, but can be very overwhelming. A delicate balance of parental guidance and child's own independent study needs to be carefully maintained.
