Trust your instincts - if you weren't imressed with the SENCo at your proposed school then chances are your child won't get the support that he needs. If you don't have a Statement to provide additional support then your child is very vunerable. Keep looking around your other secondary school choices - do you have a local support group for Autism/aspergers, you could tap into the knowledge of other parents who have gone through the Grammar system.
What the SENCo is describing is as much a sympton of dyspraxia (often co-exists with aspergers), if you think that your child may have some of these problems than seek a diagnosis from an occupational therapist by either referral from GP or privately www.otip.co.uk
. This would place your child firmly on the SEN register.
If you do decide to head for your chosen school despite the SENCo's reaction it may help you to be aware of the Disability Discrimination Act. I have posted separately on this site about disability discrimination, extract from that post
Failure to take reasonable steps
The school can also be accused of discrimination if it does not take "reasonable steps" to ensure your child is not at a substantial disadvantage compared to the other pupils at the school.
a secondary school fails to make the arrangements necessary for your child to be able to sit public exams
a deaf pupil who lip-reads is at a substantial disadvantage because teachers continue speaking while facing away from him to write on the board
a pupil with dyslexia is told she cannot have her teacher's lesson notes, and that she should take notes during lessons "like everyone else".