Tomtay1416:

My son PSLE result: English-B, Chinese-B, Math-A*, Science-A*, Aggregate Score-228.

His teacher said A* is 91-100, B is 65-75, like this the minimum score should be 234, however his teacher said this is T-score.
Why T-score is so amazing? anybody can advise me? thanks

I don't know how you get this idea that 2 A* of 91 and 2 B of 65 has a T-score of around 234. It's actually more of 216-220 (depending on the mean and the SD).

Your son's results are more likely to be something along the lines of 2 x 72s for the languages and 2 x 91s for maths and science, with an average of 81.5, or any similar combination. Again, this is a really rough estimation as we don't have the mean and SD, but the idea is there.