I typically recommend testing only if there is a function to it, not "just to know". On score changes: yes, there is some stability, and also yes, the scores may change over time. As I noted in my post to another of your threads, I have not had my children tested, but I have seen many, many records from children who were retested at multiple ages. Generally speaking, scores that are more extreme (very high or very low) see bigger changes on retest, back toward the middle (aka, regression to the mean). But very young children are also unpredictably testable, and may generate low estimates.
We had our eldest tested very young because it was formally required for early school entry consideration and encountered this problem. Although we toyed with the idea of retesting for many years, we did not act until a peculiar event drove us to do so. Another child who was tested at an older age reportedly had the highest IQ in the class and was conscientious & competitive. She could not believe that my daughter who was younger, very laid back and supposedly had a lower IQ, could outperform her in class tests and started publicly calling DD a cheat, which began to have a social impact. After we submitted the results of the second IQ assessment to the school, the accusations ceased. We never said anything to anyone about either IQ assessment, but this other student’s mother was a parent ‘volunteer’ and regularly tidied up the office area. So much for the supposed confidentiality of student records...
For many reasons, we became disillusioned by gifted programs and private schools, so whilst we also had our youngest tested as required for early school entry (& our son, even though he was not socially ready for early entry, just so that in later life he wouldn’t feel he wasn’t treated equitably), in the public school system there’s never been any catalyst for us to seek retesting, even though we suspect they were all underestimates.
