IQ tests are often administered in schools around 3rd grade or so. Earlier if a learning issue is suspected. IQ tests only tell part of a child's situation - a snapshot in time. My children have taken the Wechsler Preschool & Primary Scale of Intelligence or WPPSI for short - I don't think it is available on-line. It is very helpful to have a professional test the child and then offer an overview or interpretation or opinion concerning the results.

I'm guessing that you must suspect a problem ?? If you are interested in learning progress then perhaps what you really need are achievement type tests - which measure knowledge learned. IQ tests measure different areas and so it would not make sense to take that test more than every three or four years.

Hope this helps