Hi ReneeS1,
 
I would ask yourself (and some of your current or potential customers), "Which websites does my target market visit most often to find tutors for their needs?"  Among those, ask yourself: "which can I afford to register with, and which will deliver the biggest return-on-investment?"
 
For general reference (and follow-up research), here's a website that connects tutors with parents and students: http://www.happytutors.com/TutoringCompanyDirectory
 
Consider also optimizing your website for search engines, particularly for customers doing local searches. Don't forget direct outreach to local schools and school districts -- they may have websites and may be willing to host a link to your website for parents and students at their schools.
 
Good luck!