Tyga Alert -- Warning to Students: We Have A Tyga On The Loose

Hey Tyga, someone has a message for you ... stay away from our high schoolers!

Hanksy -- a self-proclaimed cross between Banksy and Tom Hanks -- skulked in the 'hood around Calabasas High ... and other places around L.A. ... to plaster signs warning that Tyga might be on the prowl.

Obviously the art was inspired by Tyga's relationship with 17-year-old Kylie Jenner, who does not attend that school or any high school for that matter.