let me share some info with u ah. My kid has done a similar test in 明愛 last year costly $3,000 (inlcuding 韋氏IQ test and 情緒分析). I have collected some quote from private insitution as well but I chose 明愛 at last. As a commerical institution, I was afraid the private institution can't provide an overall assessment for my son.
According to the specialist, we may have some common misinterpetation:
1) it is not recommended to do IQ test too early as some kids may not fully understand the IQ question so that you can't evauate whether he is 資優 or not. It may be done in P1-P3 if necessary.
2) nowadays, most of our kids have many chance to learn different kinds of knowledge and go abroad in early stage and thus they possess 很多知識和視野 - it makes us more difficult to identify whether he is 資優 or not as well.
3) the specialist said that 資優生 always have characteristics of 很強記憶力和觀察力, 正由於這樣, 很多時他們就引申出專注力的問題。 但她們反而關注資優生有沒有情緒問題, 這是一般家庭不懂得處理。
4) If your kid is not over naughty at this stage and going to start his primary school life, the IQ test may be done in P1 - contact the school 社工 of school and he will normall do appraisal on your kid first and he can recommend your son to do IQ test in EMB governed clinic - it is free or very cheap. But of course, you better ask your son's kindergarten to prepare a recommendation letter for IQ testing so that you can have more support to get free Govt IQ testing....