I am using this program for my 4 year old. He is a hands on learner so this is perfect for him. Very little written work. Mostly just uses manipulative to teach. I would recommend grade 1 for a K5 child. And this could be skipped all together, I am using it to get my son ready to sit and learn and prep him for "real math" next year.
I like Saxon math. Except for the Kindergarten. There were no workbooks to buy with it, some activities took awhile to find the materials needed. It was too unstructured for me. The other levels - 1st, 2nd and 3rd have been great!
l have two boys who are 4 1/2 and 3. I purchased this kit to get the boys into the routine of doing math. I love the scripted structure and the spiral nature of this curriculum. The activities are always fun for both boys and each day's work only takes 15-20 minutes. The younger one doesn't complete the activities as well, but my main goal was to establish a routine and I have been very happy with this program so far.
If your child already can count and do patterns and other simple skills, this will be too easy for them. It has been way to easy for my kindergartner (she is 5 1/2), but may have been useful when she was 4. We are flying through the lessons (several a day) and will probably be to the 1st grade book by January.