I told my counsellor at school that I have anxiety and stress and then my doctor prescribed me with risperidone is this a medication mistake?

Sounds inappropriate. Risperidone is an antipsychotic used for scjizophrenia and occasionally for bipolar disorder.It is often overused by providers for anxiety and depression for which it is not indicated.I suggest seeing a psychopharmacologist.Risperidone is a heavy drug and should not be used for anxiety and stress.Cognitive behavioral therapy, exercise, sleeping and meditation will do you more good without the risk.
Get a 2nd opinion. This is for major mental illness. Most physicians believe that meds, including heavy-duty ones like this, are greatly overprescribed in place of common-sense Rx (simple meds, talk, guidance) because of fear of liability if something happens. If you have serious mental illness & need this Rx, you have a right to an explanation. See another provider.
It's not a mistake. but you missed a piece. Please see a clinical psychologist or other mental health professional for treatment for your anxiety. A school counselor does not have the time or background to deal w/an anxiety disorder though they do lots of good work. Peace and good health.