The sites listed here provide instruction not just practice. Practice sites are great for reviewing skills and there are many of them provided throughout the posts. These sites are designed to teach your child. You will need to make an account and to assign lessons to your student. Please reach out if you have questions.
Khan Academy- offers lessons for Preschool- through advanced placement classes – https://www.khanacademy.org/
Michigan Virtual- for 6-12 grade students –https://lc.michiganvirtual.org/