Challenging behaviours are more likely to appear when a student is feeling unhappy or unwell. Medical concerns, mental health issues, or sensory responses that we cannot see might bring pain or discomfort to a student with autism that we might not understand, especially when the student is unable to say so.
Taking a step back and considering why a student might behave in a certain way is the first step toward understanding, learning how to assist the student and spotting the things that trigger the behaviour.