It's going to be a bumpy year. When you wave goodbye at the front door to your little teen-age darlings as they bound down the steps to the first day of school, remember you are sending them off to a classroom full of . . . other teen- agers. his daily commingling with peers means that your teens' use of slang (and other annoying habits) will increase exponentially in the coming month. As their language becomes indecipherable, their bedrooms will become impassable.

Herewith a back-to-school emergency primer for parents. If you hear any of these expressions bandied about the house in the next few weeks, you'll know you're already in trouble. air mail n. Garbage thrown out of a window (Martha Johnson, Purcellville, Va.). bust your grill. colloq. To hurt physically, as in "Mike Tyson could bust your grill with his uppercut" (Michael Roots, Washington). house ape n. A small child or infant (Martha Johnson, Purcellville, Va.). like a big dog. colloq. An expression used to describe something done to excess, as in "He was sweating like a big dog" (Greg Hickman, Huntingtown, Md.). neo-maxi-zoomed-dweebie (neeohmackseezumedweebee) n. A total geek, i.e., the ultimate insult (Chris Tindall, Burke). roller-rings n. The police, as in "Yo! Chill! The roller-rings are coming this way" (Louie Benitez Jr., Gaithersburg). Linguistic observers are invited to send examples of teen-age slang to: J Street, The Washington Post Magazine, 1150 15th St. NW, Washington, D.C. 20071.