A report issued this week by The Pioneer Institute, a Boston-based a public policy think tank, sheds light on the rapid growth and diversity of the U.S. homeschooling population.

Co-authored by William Heuer and William Donovan, the comprehensive white paper explains that despite a paucity of support from government officials--and outright opposition by the nation's largest teachers' union--homeschooling has gained in both popularity and reach over the past several decades.

According to the latest 2012 National Center for Education Statistics (NCES) data, there are over 1.8 million homeschoolers nationwide, representing 3.4 percent of the overall U.S. K-12 school-age population. More recent data place the number of homeschoolers at well over 2 million children, placing it on par with the number of children currently enrolled in U.S. public charter schools.