With the obvious caveat that I'm not a medical professional...
Some of the children of parents in our local gifted advocacy group have found themselves in a similar position, with schools seeking to have an autism spectrum diagnosis put in place in order to secure additional funding to support the child's learning needs (by hiring an educational aide, for example, for the classroom). Some parents have Asperger's/gifted kids, but others have done autism assessments that have produced an array of results from speech pathologists, occupational therapists, and educational psychologists: auditory processing issue; ADHD; sensory processing/coordination issues; depression/anxiety/OCD; and of course simple gifted overexcitabilities/intensity. So my sense is that autism may be a bit of a diagnosis-du-jour for some school professionals (and I mean no disrespect to the many kids and parents dealing with ASDs, but I'm really concerned about the fact that schools are generating this suggestion).
My advice would be to seek a comprehensive assessment by someone who is familiar with gifted kids and with kids on the spectrum. There are some overlapping behaviours--the Webb book on misdiagnosis/dual diagnoses is helpful--that could be examined. And your child's pediatrician is a good place to start, too; if exams up to now have not turned up any indicators for autism in terms of developmental issues than it seems unlikely that it would first manifest at school, doesn't it? Best wishes.
