WHEN YOU CONSIDER that John McEnroe spent his first childhood as a student of the Nastase-Connors School of On-Court Tantrums and Digital Communications, the way he is spending his second on Wimbledon's Centre Court is neither original nor surprising. His elders may have gone on to better behavior, making this an exmaple of life imitating art. Besides, when you're seeded No. 2, you try harder -- which may help to explain why Mr. McEnroe tried the patience of just about everyone on hand Monday at the All England Lawn Tennis and Croquet Club.

At 22, Mr. McEnroe doesn't behave a day over 16, which may be perfectly all right with the new wave of romp-and-stomp sports fans who love a little rough stuff and showmanship in any event they've paid to see. But at 104, Wimbledon is just a bit old for the infantile and obscene racket-smashing and name-calling performance by Mr. McEnroe on Court No. 1. It is stuffy, yes, but you don't spit in Grandfather's face and call him names, and, as staff writer Thomas Boswell noted yesterday, you don't call an umpire at Wimbledon "an incompeent fool," nor do you call the head referee "an imbecile." You don't call the umpire and his crew "the pits of the world," either; nor do you utter a four-letter expletive on the court.

All this, coming after cursing a lineswoman at the Queen's Club two weeks ago -- and then hitting a ball at her -- has made Mr. McEnroe less than a Beautiful American abroad -- even with that old disclaimer that "the views expressed do not necessarily. . ." And contrived or not, it's not funny. The Bad Seed of tennis should grow up.