Is this right?

My nephew, 25 month, was in the same class, book 1 playgroup class, with Megan in their school before. They learn simple phases such as: I love my mummy, I can jump, etc which the main point is to help children to understand the meaning of pictures and words such as drink, bath, jump, etc.

But start from this semester while Megan are learning alphabet and continue the book 2, he was move to book 3 class, this poor boy has to learn sentences and simple math such as 1+1=2. His classmate are range from 2.5-3.5 years old and he's youngest but not the smallest cause he's tall.
The most irritating was, they didn't even discussed this with the parents, they just decide it by themselves so my cousin just accidentally knew about this a few days ago.

When she phoned school and asked about it, they said he is already 29 month so he need to mingle with kids that already able to talk well to influence him to talk and they said he's tall and big so will fit up better (of cause la with 3 years old kids).
They also added that if he is not able to catch up, they'll moved him to book 2 class later.

For me, the reason is quite stupid because, in class room, children not only learn to talk but many others skill. Also the school didn't considered the psychological effect on the boy now he refuse to go to school which was never a problem before.
I always thought that if a child is exquisitely smart, he can be moved to a higher grade depend on his/her brain ability so he/she will be continuously challenge and learn a lot.
But this concept seem does not apply in this school.
My nephew is not one if them, he still can't speak in age of 25 month (although he understood almost every words) and he has concentration problem.

Maybe because of administrative works, they refused to move him to book 2 class right when my cousin asked for it. But isn't they caused all this by themselves for being arrogant and ignorance?

Is this normal in preschooler? please advice.....