S.H.
*Adding this: If you do decide to keep your son at preschool for a bonus year, make sure your older kids do NOT "tease" him about it. There is no need to. And if they have questions about it they should ask YOU... not him. He will not know how to explain it.
My daughter did ask why her 2 classmates (per below) was still in preschool or Kindergarten, when she had gone on. I simply told her that everyone is different and their Mom decided that that grade was best for them. And it does not mean that it is better or worse. Everyone has a different time to graduate onward.
*First, make sure that you DO want to keep him there, for the bonus year. You said he is 'smart' but has LOADS of energy. Well, most boys do. So is this the only reason, for keeping him back? Or is it his overall emotional "maturity" and numerical age? If his maturity is fine, and his skills...then it may be okay. Has his teachers recommended he stay back? Have you asked them? Is he a good student presently and can listen to direction/follow instruction and cooperate?
That exact same thing, happened with my friend and her son.
My other friend, also had the same thing happen with her daughter. Both are late-born as well. For these friends, one kept her son back due to emotional maturity/readiness. For my other friend, she just wanted to keep her daughter at preschool longer because she did not want her daughter to grow up too fast or feel school stress already. Which, her daughter is quite fine and mature and academically ready.
BOTH kids are perfectly fine! They did their "bonus" year of Preschool, and the other classamtes went off to Kindergarten at different schools. Presently, they are now in Kindergarten themselves, while the other kids in their class (like my daughter) is now in 1st grade. It was NO PROBLEM for either child.
In fact, they are totally enjoying Kindergarten now, despite their other classmates being in 1st grade, and seeing each other on campus. And they had NO problem "still" being in Preschool while the other classmates left to go on.
I'm sure he will be fine. Sometimes, we just worry for our child and it's TOTALLY normal, for the Mom to do so. But, as I saw in my friend's children... they had NO problem with it whatsoever! It was mostly the Moms that were worried and over compensated.
My friends just explained to their children that each kid is different and that as a Mom, they feel that staying at their preschool was nice for them etc. But really, it took no extra sort of "convincing" the child or anything special. They just simply told their child that they will still be at their preschool next year, that every child goes on to Kindergarten at different times. The Teachers though, ALSO explained to the children about "school" and how each year each child has different schedules.
MY daughter is late born as well.... but per her maturity level/school readiness, AND her teacher's input... we let her go on to Kindergarten. She was 4 yrs. old almost 5 at the time. She is now in 1st grade where she turned 6 yers. old. She did not suffer at all in any way from being in school. She even told us she wanted to go on. It has worked out, and my daughter is happy and does well in school.
Don't worry.
It'll be okay.
All the best,
Susan