Television networks are not usually in the business of telling viewers to get out of their easy chairs, turn off the set and go do something more worthwhile. So the campaign announced recently by the American Academy of Pediatrics to warn children against becoming couch potatoes by spending too much time in front of the tube deserves a wholehearted endorsement.

The 30-second cartoon shows a boy and girl turning into couch potatoes while lounging in front of their TV. "Avoid this dread disease, be choosy in what you watch," the announcement warns. "Don't just plop in front of the TV `cause you've got nothing else to do."That's great advice for people of all ages, and ABC and CBS, which have announced they would run the announcement, show a lot of public service spirit by agreeing to show it.

Television, like anything else, is used best when used in moderation. By encouraging young people to develop selective viewing habits, the industry will help raise a generation able to discriminate between good programs and bad; in the end, that will help everybody.