Breitbart, if you can trust such as source, and the president does:
However, that number only includes those involved in an individual learning pedagogy involving children and likely does not include an adult self-learning andragogy. The 15% I used represents the area where homeschooling is likely applied .
According to data published on May 7 by the National Center for Education Statistics (NCES), in 2003 1,096,000 school-aged children were homeschooled in the U.S., representing 2.2 percent of the total number of students in that age range that year. In 2012, the number homeschooled was 1,773,000, or 3.4 percent of elementary and secondary school-aged children that year.