We did regular school ... like your son, mine never complains either- and he developed mechanisms to blend in perfectly ... down to manipulating grades and test scores to match the rest of the class ;-) We never had an problems with regular school besides being stressed and getting migraines.
Now we homeschool and do an enrichment program ( non TAG - mostly STEM) with other homeschoolers one full day a week for socialization and fun and a break for both him and me. My son does miss not being around so many kids all day long as he is social but he appreciates getting done with his regular school work fast. I never worried about acceleration as much as his happiness. The problem for my son is the curriculum itself - he is in 5th and can understand and do highschool math but ... it is not exactly his passion. Science on the other hand is a joy for him and he much rather learns everything there is to know about some exotic insect rather than puzzle on advanced algebra. At home I am able to give him things he is interested in in addition to the curriculum. Schools can advance him in curriculum but even at several grade levels above the content is not necessarily in depth and interesting enough. Unless I would have him take highschool classes there is no way to really introduce things he perceives as fun and interesting ... biology, stem cell research, physics, chemistry, genetics, botany and even philosophical discussions. We don't necessarily work grade levels ahead in school subjects ( well maybe 1-2) but add extra things and go into more detail and learn things that are never taught in school at all. That is in my opinion the greatest advantage of homeschooling ... there are no restrictions and if you feel like writing a 5 page research paper on the pacific squid ... there is nobody to give a time limit or tell you that this is unusual or make you feel weird ...
