I have a 12yr old boy who I am homeschooling because he hasn't learned the basics at school. This includes reading and writing. He has a cognitive processing disorder which means that he can learn it but can't always get it back out. It gets jumbled in his brain. I also have a 10yr old girl who is very advanced. She loves learning and is having no trouble. Can I teach at the same level together? For example year 6-7 work, even though he should be year 8 and her year 5?
Children learn at different rates anyway. You seem to be aware as to the capabilities of your children. If your 10 year old can handle more advanced work then definitely give it to her. Just make sure that you test her regularly so that her comprehension level of each subject can be assessed. As for your son, start with the basics, again regularly assess what he has grasped and move forward based on this. Forget what year level he is supposed to be in. Work with him based on his individual needs now. You will find that your daughter will move ahead rapidly you may want to plan a lot of work for her to extend her. I find that reference books help with this to expand vocab and comprehension. Set her specific projects that interest her.
Hope this helps.
V in Australia