Rosanna Ward is a passionate advocate for home schooling. She devotes hours a day in her Tulsa, Oklahoma, home teaching her 8-year-old son, Joel.

"You can tweak your curriculum and your teaching style more to the way your child learns," she explained. "For me, it's an awesome and fulfilling thing to be there when my children are learning."

Ward has some experience. She home schooled her two daughters Ginny and Hannah, and was home schooled herself as a child, which was rare enough at the time that it earned her a picture in the local paper.

In 1980, when it was largely seen as a faith-based fringe movement, home schooling was illegal in 30 states. By 1993, it was recognized as a parent's right across the country. And today, Ward's son is among the nearly 1.8 million home-schooled American children, according to the Department of Education. That's more than double what it was two decades ago, and matches the number of children enrolled in public charter schools. Uniting religious conservatives, progressive "unschoolers" and parents simply fed-up with their local public school, home schooling has become a mainstream educational option, with the reasons for why parents choose it, and the resources, support groups and curriculum available to help them, growing every day.

Despite its explosive growth, home schooling is still a remarkably deregulated enterprise. Half of all states require parents to simply register their intent to home school, and 11 states have no regulations at all. It’s hard to do a comprehensive count of home-schooled students, when in many places, they don’t have to notify anyone that they exist.

Though many home-schooling families and advocacy groups, including Ward, credit the lack of regulation with providing more flexibility and space for creativity, some critics charge it can leave children vulnerable to educational neglect, and even abuse, with few ways of finding help.