CBS, like the other networks, waxes adolescent as often as possible. But tonight its prime-time schedule actually concerns the teen-age years, rather than just pandering to peach-fuzz mentalities. All three hours of it are worth respect and attention, though in varying degrees.

"Boys and Girls Together," the "CBS Reports" broadcast at 8 on Channel 9, looking with justifiable alarm at collapsing moral codes of American youth and the rising rate of teen-age pregnancies that is a direct result. A genial cop who has just coaxed some 16-year olds away from a California beach late at night notes, "Sex to them is nothing. It's like going to the store."

At 9 on Channel 9, things get considerably preachier with "The Boy Who Drank Too Much," a fictional film about a teen-age drunk that is more heavily laden with lessons than with dramatic conviction. It often works effectively, though, as the story of how far people will go both to hurt and to help one another.

"Boys and Girls Together" deals with material undeniably pertinent and probably urgent, and yet this CBS News hour has been-sitting on a shelf for a year now waiting for programmers to find it air space. Such sloppy priorities may be deplorable, but the picture painted by the program is not likely to have changed much in the intervening months.

Correspondent Harry Reasoner, who co-wrote the script with producer Andrew Lack for Howard Stringer's unit at Cbs News, says at the outset that 2,000 teen-age girls get pregnant each American night and that one out of five teen-agers has has intercourse by age 13 or 14.

After that, we are off on a round of interviews with teen-agers like Cassandra, pregnant at 15 ("That's okay," she says meekly, upon learning the news); a 13-year-old girl who recalls how fervently a boy propositioned her when she was 11 and just getting out of the sixth grade; and a dubiously typical family from San Francisco's trendy Mill Valley, a hotbed of hot tubs where people talk in cliches about "stress" and "relationships."

Some of it is both chilling and valuable, but perhaps the most trenchant analysis on the program is allowed just to slip by. That is Dr. Brown Hawkes' assessment that the apparent sexual anarchy among American youth is partly the outcome of living in a society in which kids are continually bombarded with sexually suggestive messages.

This is what Dr. Hawkes says:

"I think some of it's the media's fault. I think these children sit back and see TV and they say, 'Well, that's great for the adult; let's have a little bit of the action ourselves.' They can't listen to a rock 'n' roll band and not hear suggestive passages.

"The whole climate these days is sexually oriented, and it's oriented to people that don't understand their own sexuality. All they understand is the fun that goes with it, not the seriousness that follows it."

Some of the visuals used to illustrate this report are bound to strike viewers as titillating themselves, especially a bikini contest in New Jersey, intercut with scenes from the Miss America Pagent and its celebration of values that appear now to be the exclusive domain of the Miss America Pageant. It's all a question of the value people put on themselves, says Reasoner in his wrap-up, adding that this documentary isn't going to end with the usual "upbeat ending" because "We couldn't think of any."

Of course, upbeat endings have been inappropriate to many other network news programs that got them anyway, but this is still a commendable gesture.

"The Boy Who Drank Too Much" suffers from the fact that teenage alcoholism is such an "in" subject on TV this year. No one has yet surpassed "The Late Great Me: Story of A Teen-Age Alcoholic," an ABC Afterschool Special seen in November.

The topic has even been brought up in such insipid and inadequate forums as "Hello, Larry" and "Eight is Enough."

As the boy in question, Scott Baio (of "Happy Days") does a serviceable if mumbly job, but the character seems sullen and antagonistic from the start. So it is hard to understand why a friend, played by Lance Kerwin (once "James at 15") goes to such pains to help him recover from his disease and rejoin the school hockey team.

Also, the screenplay by Edward Belasio comes up with a pat, 11th-hour explanation for the boy's alcoholism: He blames his father, also an alcoholic, for the death of his mother and, oops, it was all a mistake. He skates off into the distance, miraculously cured.

Nevertheless, as the portrait of a friendship that has to face the toughest of tests, the drama is often touching and unusual. Kerwin's portrayal of an old-fashioned honorable kid -- one with more faith in his fellow man than his parents have -- is thorough and encouraging and an antidote to the hopeless outlook put forth by the teen-age sex show earlier in the evening.