I'll add that, though the tics appear mild, it may be that his efforts to control them during the school day are exhausting all of his EF functions, which leaves him much more vulnerable to outbursts by the time he reaches home. You might consider investigating CBIT (cognitive-behavioral intervention for tics). Check the TSA website for info. Some CBT basics are also generally good for developing coping skills, especially where anxiety appears to be in play.

...pronounced like the long vowel and first letter of the alphabet...