I would question why they are raising this so early in the year? A child changes so much in the span of 12 months. Normally we would start to consider a child's readiness towards the mid to end of 3rd term.
I would suspects he has missed out a bit staying in the toddler room and then skipping up to the preschool room - in my experience children are usually really ready to go up to the next age group from our toddler room as they do need the extra stimulation and 'routine' that comes with the older age group.
I would give him a bit more time before you make any big decisions - school may be exactly what he needs to extend him further. I would advise, unless you are seriously concerned that he won't cope, I would never hold a child back from starting school at the correct age.