Hiding Out

Hiding Out is a 1987 movie starring Jon Cryer as a states witness who is forced to disguise himself as a high school student in order to avoid being killed by the mob.

Needing a safe place to hide, Andrew, under disguise, attempts to contact his cousin, Patrick, played by Keith Coogan and aunt portrayed by Gretchen Cryer, Jon Cryers reallife mother, arranging to meet the latter at the high school at which she works as a nurse. While sitting in the nurses office, he impulsively opts to enroll, taking the name of Maxwell Hauser off a Maxwell House coffee can and begin high school all over again. He pulls his cousin aside and reveals himself, eventually using Patricks house to sleep in, unbeknownst to his aunt.Not willing to take the attitude of teachers, Andrew becomes a hero to those tired of the schools status quo, which upsets Kevin ORoarke played by Tim Quill, the current class president, and captures the heart of Ryan Campbell Annabeth Gish. During an afternoon at the local diner, he accidentally drops a birthday card meant for his grandmother who had raised him and it gets mailed. Later, a hitman posing as an FBI agent contacts his grandmother and sees the card and its postmark, telling him where Andrew is hiding. ........

Source: Wikipedia