My 2 year old is also asking this... Big brother has just started reception.
Its tough on those who just fall either side of the cut off, I know some who had to start school, and some who have just missed out. In a few months it will all settle back down. BUT a cut off has to fall somewhere. It happens to fall in Sept.
Poor ds can't understand why he can't go to reception like his friends. He's nearly 4, his main friends from his last preschool have gone to 3 different schools, he is now at a nursery attached to the school he will go to. He seems to have settled well, is very pleased to have homework, a reading record and books to take home, but what he really wants is to be in reception. He has some good friends in his new nursery whom he already knew, so I don't think it is that, he just wants to be older. He is nearly 4 so some of his friends are only a month or two older than he is. He asked about it three times today.
I am happy to have him for another year, he is funny, generally easy going, considerate and enjoys shopping. I just feel sad for him that he is so clearly wishing to be in a different year group. He even asked if he could go to reception in x's school instead of waiting until next year.