Hi there,
I am no expert at all on this (nor was the person who assessed my 3 year old), I should disclaim that first.
Congrats on some great scores. Your little one is clearly bright!
Like others have said its just the measurement on that day. With 3 year olds it can depend on their attention span, how they test, how they feel about the person giving the test etc.
I disagree that there are no children with over 135. Our little one was tested at 3 years 5 months and ceilinged 4 of the 5 subtests with an IQ in excess of 145 (greater than 99.9 percentile) so i am certain it does exist.
I have been told that it can change over time but I am not sure about getting better with age. My understanding was that it could go up or down for various different reasons.
You have no need to be disappointed as your little guy sounds like he is done wonderfully
