In general, about 8 years old is recommended as the time when IQ scores may be stable... and would not tend to vary much on any subsequent testings.

However, testing is also done at younger ages, especially when parents are seeking to understand something out-of-the-ordinary which they may be observing about their child.

The test(s) which you choose or suggest/request in working with your tester depend upon your reasons for testing. For example: Are you planning to apply to a specific program? The tests which are accepted for the Davidson Young Scholars (DYS) program are listed here.