Dr. Robinson has created a curriculum or educational program that truly is not based on “grades.”
The student/child is advancing through a series of math books, writing daily, studying, and reading a course of chosen literature at an individual pace. The literature to be read is put in an order from simple to advanced levels and you can choose where to begin by using your own judgement as you view the books on the screen, based on your knowledge of your child’s age and reading ability. I would not worry about starting an older child too early in the reading selections as most of the books are enjoyable and worth reading at any age.
A more objective way of placing the student is by using the vocabulary flash cards to determine their reading comprehension level.
Each book in the core read order has a corresponding vocabulary. Choose a place in the read order and if they do 80% or better on the first pass through the vocabulary flash cards (Words and Definitions) they can skip ahead in their reading. If they get less than 80% correct you should skip back. Keep on testing till you find their level. (They should master all the vocabulary words regardless of where they start.)
For Math, Saxon Publishers have available math placement tests. Or, if you have them available, use the tests that come with each textbook.
See Placement and Testing for more.