Clonazepam is addictive. Both medications you mentioned are anti-anxiety.
An uncontrolled tic not removed by behavioral "therapy" is likely a sign of enormous anxiety. I bet some of the anxiety sources can be removed and then the tic would get better.
We can look for them, starting with answering some questions:
What therapies and services does your son receive? What kind of school does he attend to? How is he doing? What does he like/enjoy to do? What are his interests?
I think that would be a nice starting point. Cheers!
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Let's not confuse being normal with being mentally healthy.
<not moderating PPR stuff concerning East Europe>