I want to add that my son does the same exact thing and we ignore it. Drawing attention to tics is the worst thing you can do. It doesnt sound like its a constant thing overwhelming his ability to function. Tic disorders are extremely common in boys esp intelligent boys.
Watch out because in all likelihood your son will be diagnosed with Aspbergers and ADHD neither of which I think is the case. It is very common for boys to suffer from tics and it usually doesnt remediate entirely until the teen years when CNS achieves full maturity. In another time period, people didn't get so bent out of shape over this. I think very bright children suffer disproportionately from attention issues (usually because they are bored) as well as some physical tic-king. He is still very young. I would try to work on his issues as a matter of habit and give him cues at home that he might transfer to school. But be proud of having a gifted kid. You can try contacting Stephen or Mary Camarata of Vanderbilt University who have worked with thousands of children just like your sons.
He should be evaluated by a pediatric neurologist to rule out any seizure disorder or disorder involving involunatry muscle movements (tics). After that evaluation, depending on the outcome, he should be evaluated by a child psychiatrist to consider a disorder of attention.