Hi Endy,
 
I recommend you contact U.S. Citizenship and Immigration Services (USCIS) to find out rules specific to the visa you do have. Here is their National Customer Service Center hotline number: 1-800-375-5283. They also have Law and Regulation information on their website: http://www.uscis.gov/portal/site/uscis
 
Once you've confirmed that it is legal for you to participate at an elementary school as a volunteer teacher's aide, you can research U.S. schools in your area through SchoolFinder:
http://www.education.com/schoolfinder/
Contact schools that interest you to see if they have a need for a volunteer teacher's aide, or if they know any other local schools that do.
 
Information about the teacher's aide profession is available on the Bureau of Labor Statistics site here:
http://www.bls.gov/oco/ocos153.htm
 
Here is a listing of teacher's aide learning institutions (including universities and colleges):
http://www.edref.com/college-degrees/education/teacher-aide/online
 
Here is information about teacher's aide certification:
http://www.edref.com/college-degrees/education/teacher-aide
 
I hope these resources are helpful to you and that you're able to achieve your goal.