Preschool? Kindergarten?

It's the time of the year to register for next year's class. Without doubt, Jay is going to playschool. He has been telling everyone that he is grown up and he wants to go to school. I think this is because he has been watching his sister enjoying going to school, and he does get rather lonely at home with granny. The day I brought home his school uniform and tried it on him, he did not want to take it off! He wanted to go to school right away! He had to put on the uniform again when daddy is back from work in the evening. He looks so grown up in the uniform, I had to try very hard not to drop any tears. It's the same thing with Joy last year, when we decided that going to preschool might help with her socialization and her speech. My babies are growing up.
This time, I had a scare with Joy's registration. The head teacher suggested that perhaps I should consider letting her stay in preschool class when she is supposed to go to kindergarten 1 next year. Daddy and I were so against it, since Joy has been learning the alphabets, numbers and shapes taught in preschool since last year! She will be bored if she were to repeat the same thing next year. I admit that she has not been doing her quarterly school test. she needs one to one attention to finish the test and the teacher does not have the time for her. Despite this, her class teacher and I know that she is listening in class, and understands what is being taught. But of course, with her still being non verbal, she did not talk about things she learnt the way other students do. Should this be the reason for her to stay in preschool? I should think not! Besides, she has her own circle of friends who are at the same age. I would not want her to start anew next year trying to make new friends. She took 3 months early in this year before she warmed towards the teacher and her classmates. Since they have accepted her as she is, I hoped that their acceptance would help her to continue to improve instead of having to gain acceptance in another new class and wasting time.
To me, Joy has only these critical kindergarten years to learn the rules and structure of being in school. I hoped that with time, she would be able to fit in primary school when the time comes. At the same time, I am preparing and training myself to provide lessons at home to make sure her academic does not fall behind. It's not easy, having to handle a full time job.