For years, I've been getting letters about it. For years, I've been ignoring them as the mutterings of the thin-skinned and the grumpy. But now, I ignore no more.

The other day, I had to get from Someplace to Some Other Place at about 3 p.m. on a weekday. So I hopped a Metrobus -- at which time I stepped directly into a madhouse.

It's true: teen-agers going home from school on the bus are a bunch of maniacs.

Here's what happened in the space of 15 blocks:

* One of the boys yanked the pigtail of one of the girls. She retaliated by bopping him across the forehead with a biology textbook. To reach him, she plowed through three female standees each of whom had to be more than 70 (that's right -- none of the kids had offered any of the ladies a seat).

* Two boys got into an argument about basketball. One of the two had a basketball with him. He proceeded to demonstrate his point by slam-dunking the ball against a cigarette ad. He left a dent in the ad -- and the wall -- about three inches deep.

* One of the boys wanted to get off at the next stop. He pulled the bell-string 15 times (I counted -- how could I help it?).

* Three girls had a giggling fit. If you're a teen-aged girl, a giggling fit is always followed by a careening fit. As in laughing so hard that you lose your balance. As in falling into some guy's lap and totaling his copy of The Arlington Journal in the process.

* Last but not least, four boys in the rear seat recognized somebody on the sidewalk. As the bus waited at a red light, the four riders opened a window (on a 30-degree day) and pelted the pedestrian with ice from a cup of soda -- which they shouldn't have had on the bus in the first place.

Now, I admit that I get closer to being a fuddy-duddy with each passing day. And I admit that one bus ride on one day may not prove much. But I asked several bus drivers, and they say this kind of thing happens all the time.

One driver said the only question is how bad it'll be each weekday at 3, not whether it'll happen. Another driver said he has asked to switch to night work just to avoid the daily madness.

Transit cops ride subways all the time. Isn't it time they hopped a bus once in a while, too?