Parents always want their kids to do better on tests. A large number of adults returning to school are also looking for an edge.

Given the low barrier to entry, this field is competitive. But if you carve out the right niche, it could be lucrative.

The industry, which includes tutoring in such fields such as special education, language, and music, grew about 7 percent last year, according to AnythingResearch.com. 

By the numbers:

Growth in 2009 sales for "other schools and instruction," according to Sageworks: 11.82 percent

Ranking of "exam preparation and tutoring" in AnythingResearch.com's "fastest-growing industries that are hospitable to small businesses": 7

Year-over-year growth rate, according to AnythingResearch.com: 7 percent