Or, they may feel like they are being punished for being smart by having to do more work. This is an outstanding option for parents who can do it. Kids these days don't learn socialization skills at school, they learn anti-socialization skills. Often gifted children and children identified as ADD take the brunt of this sort of abuse and may be traumatized for life. There are plenty of socialization opportunities for homeschoolers, including sports, clubs, playing with friends, camps, volunteering, etc.
Homeschooled children are, on average, ahead of their peers academically, often by several years.
And they spend less time studying because there is less time wasted. Gifted children usually do very well when they are homeschooled. The specific requirements for homeschooling vary. In the U.S., check with your state. In some regions, children are allowed to attend public school on a part-time basis.