Rebecca Black -- Yanked Out of School After CONSTANT Harassment

Rebecca Black was getting made fun of at school SO MUCH after "Friday" came out -- that her mother decided to pull her out and began homeschooling the singer.

Black just told ABC News ... students were constantly targeting her, explaining, "When I walk by they'll start singing 'Friday' in a really nasally voice ... Or, you know, they'll be like, 'Oh hey, Rebecca, guess what day it is?'"