I'm curious if an experienced psychologist who works with a large population of gifted children and administers IQ tests is able to estimate a child's IQ with any accuracy (without doing an actual test).

I am asking because my son took the WPPSI last fall while applying to a gifted school that required it (he was wait listed). The test was at the school and administered by a psychologist who contracts with the school to do the tests. His VCI was very high but fluid reasoning was 27 points lower. His FSIQ was in the 99th % but lower than we had expected. We later learned that my son didn't cooperate with parts of the test, became frightened and acted very strangely.

My son spends an hour a week with a psychologist to work on his social skills. The psychologist has known my son for a year and has not only spent lots of time with him but also observed him at school. She is the person who recommended the gifted school and thinks that no other school in the area can really accommodate my son's needs. She believes the WPPSI was inaccurate because of the feedback about my son's behavior but also because she works with lots of gifted kids and said the number just didn't reflect her observations and knowledge of my son. She believes he will score much higher if retested.

I'm asking because my son's psychologist has recommended that we have another test done once a year has passed (from the last test) and once my son turns 6 and can take the WISC. She has recommended some psychologists who she thinks highly of. She thinks that if the test is done well with a good psychologist who takes time to develop a rapport with my son that we will receive a very different result and perhaps be successful if we reapply to the school.

I hate the idea of spending money for new testing. I'm guessing it will be at least $1,000. Technically we can afford it but it's a large amount of money to spend if there isn't any reason to. So I'm hoping that somebody with experience can tell me whether our psychologist is likely to be right and my son will have a very different score upon retesting or if we need to just forget about this school and move on.