Quarterback Tim Tebow, shown here praying before a 2011 NFL game, is perhaps the nation’s most famous home-schooled student. (Julie Jacobson/AP)

Just 13 states and the District require home-school instructors to have minimum qualifications, in most cases a high school diploma.

The other 37 states have no such requirement, according to a recent report by the Education Commission of the States that highlights wide variations in rules governing home schooling across the country.

Twenty-three states and the District have attendance requirements for home-schooled students, and fewer than half of the states — 20 — require an assessment of home-schooled students’ academic progress. Just 12 states require home-schooled students to take a standardized test, a marked departure from federal K-12 law that requires annual testing of all students in grades three through eight and once in high school.

Though home-school rules have received criticism for being too lax, many advocates of home schooling say their movement is built on the notion of trusting parents to understand and provide the best education for their children.

“A parent does not have to be highly educated in order to homeschool successfully, but regardless of academic credentials, the motivation to further one’s self-education needs to be there,” home-schooling proponent John Rosemond wrote in his syndicated column Thursday.

J. Michael Smith, president of the Virginia-based Home School Legal Defense Association, said research has shown that the home-schooled children of less-educated parents do just as well on standardized assessments as those with better-educated parents. “As long as they’ve got this love of learning, they’ve got all” they need, he said.

The report also says that home-schooled students are increasingly taking part in online schools, virtual charter schools and other online education options, many of which are paid for with tax dollars.

“As more students seek out opportunities through state-sponsored programs, students are pulled under the canopy of state standards and the lines between home schools and public schools are becoming fuzzier,” the report says.

While home-schooled children are a still tiny slice of the nation’s students, their numbers have jumped over the past decade, rising from about 1.1 million in 2003 to 1.8 million in 2012, according to federal data released in May.

Long seen to be an option favored by parents seeking to give their children a religious education, home schooling has been attracting a more diverse group, according to federal survey data.

In 2012, about 64 percent of home-schooling parents said they wanted to provide their children with religious instruction, down from 72 percent in 2003. In the 2012 survey, religion ranked fourth among the reasons parents gave for choosing home schooling.

The top reason was concern with the environment of the nation’s schools: Twenty-five percent of parents said this was the most important factor in pushing them to choose home schooling. Second was “other reasons,” including family time, finances and distance. In third place was dissatisfaction with the academic instruction offered at schools.