Hi Ki28, I can sympathise as we had some mixed messages too. DS was DXed as mild ASD with aspergers type presentation earlier this year shortly before he turned 5. Came as a total shock as whilst we acknowledge he has some issues at school we had never in a million years suspected ASD.
Our paed described it to us like this: there is a 'social scale' on which we all sit somewhere (massively outgoing 'social butterflies' at one end, the far less outgoing but socially competent engineer/mathematician/scientist types at the other, everyone falls on it somewhere at either end or in the middle, and beyond the 'engineer' type there is a line beyond which someone's social interaction is impaired enough for them to be considered ASD at whatever level of severity). She then went on to say that it was her belief that starting school had prompted DS's behaviour to tip 'over the line', as it were, from the scientist/mathematician end of the social scale where he naturally sits into mild ASD, but that it was her belief that he would as he grew older develop the ability and maturity to cope with situations better and 'cross back over the line' as it were into 'normal'. (If that sounds confusing - we were massively confused too !)
My understanding is that children do not 'outgrow' ASD but they can, depending on their level of severity/ability, develop coping strategies and I guess 'grow out of' some of the traits (although they cannot 'grow out of' the disorder itself). The thing is that a lot of children who are not clinically autistic show autistic traits - one outreach worker I spoke to told me that she could probably go into any primary school classroom in the UK and pick up autistic traits in half the class. So I guess your DS's school are keen not to label too early, which is the right approach to take, but at the same time it is hellish even having the seed of worry planted in your mind.
I guess the key issues is - what do you think? You know that little boy better than any SENCO, paed, teacher etc. Has his behaviour ever given you cause for concern? Does any of what they describe to you ring true at all? Are they suggesting formal assessment?
At the end of the day there is always the argument that as long as they get the help they need it does not matter what the label is. But it is still so difficult when the suggestion comes as a total shock. I sympathise hugely. For what it is worth, the professionals seem unsure about my DS too (and as his parents we in our heart of hearts don't believe he is ASD). I think sometimes when they are so 'borderline' (i.e. to all intents and purposes happy and settled but just showing some difficulties in certain areas) it can be harder both to DX and to accept a DX.