I would have thought not unless your visit was preceded by a series of assessments out of which your doctor came to a final decision. Diagnosis of children with bipolar is a hot topic that is receiving quite a lot of attention. It is probably more common for children who display hyperactivity or aggression to be diagnosed with ADHD but there are concerns that misdiagnosis (and subsequent medications) can make a child worse if in fact they have bipolar.

I can't offer specific medical advice but the fact that you have posted your question here seems sufficient to suggest that you are concerned - and rightly so in my view. It may well be that your doctor is right but my advice would be to seek a second opinion from a doctor who specialises in the field.