You may want to look into expungement. I'm not sure what state you are in so you better speak to a legal professional. Often felons and ex-offenders require some legal assistance before looking for jobs. I suggest contacting your local legal aid office. You may qualify for low-cost or no-cost legal assistance.
You can always contact the school board where you wish to teach to find out if your conviction would exclude you from employment consideration. If you find that it will, you should try private schools. They usually have fewer restrictions than public schools.
I hope this helps.