Hi Sorka,
Dachlostar is right, a year makes a huge difference at that age. I don't think you are biased because you are his mum, it is because you ARE his mum that you will know when he is ready. Don't send him if you don't have to just yet. But if and when you do talk to his teacher an see what suggestions they might have to help ease him into school. You may be able to attend school with him for a while.