TMZ has learned 13-year-old Prince and 12-year-old Paris started at The Buckley School in the San Fernando Valley on Wednesday.
Family sources tell TMZ ... Prince wanted to go to Buckley to have "a social experience." Initially, Paris was reluctant but changed her mind in a big way.
As for 8-year-old Blanket -- he's still going to be homeschooled. Katherine Jackson feels he's too young to venture out.
Among the alums -- Matthew Perry, Alyssa Milano, Nicole Richie, Nicollette Sheridan and Laura Dern.
By the way, some other grads even went on to do sex tapes and became famous -- Paris Hilton and Kim Kardashian.