Not perfect, not revolutionary, not always deliriously urgent, "James at 15" is still the most respectable new entertainment series of the season. Consistently, it communicates something about the state of being young, rather than just communicating that it wishes to lure young viewers.

And if it romanticizes adolescence through the weekly trials and triumphs of its teen-age hero, at least it does so in more ambitious, inquisitive and authentic ways than the average TV teeny-bop.

On tonight's program (Channel 4 at 9 James Hunter faces his gravest crisis yet. An old pal from Oregon comes to visit him in his new Boston home. It doesn't take James long to realize something is wrong. His friend is very sick, with a form of cancer, and, before the hour is over, dies.

Though a rare occurence for a weekly series, such a situation - the death of someone close - has been the basis for several TV movies. "Brian's Song" probably launched the genre. But except perhaps for Mark Hamill's performance as the younger brother of a dying boy in NBC's "Eric" special, no TV treatment has equaled tonight's edition of "James" in seeing death through the eyes of youth.

Ronald Rubin's script is perceptive to the rhythms and moods of youthful friendships and to the privileged isolation of the adolescent. For James, this is a tragedy no one else in his family can really share; and when he finds the strength to deal with it, in the final moments of the program, it's a believable personal victory.

Every week there has been something to admire and much to enjoy in "James at 15" and yet, like other good shows of the present and past, this one is IN TROUBLE. Although a smash hit as an NBC movie-plot last summer, ratings have been poor since "James" became a weekly series in November.

It's not that the competition - chiefly ABC's "Barney Miller" and "Carter Country" - is so good, but rather than the competition is such easy viewing. Viewers may not choose the "least objectionable" program so much as they do the least troublesome one, and neither "Miller" nor "Carter" requires any intellectual or emotional investment of any kind. They are programs that even do the laughing for you. "James" asks more.

Still, NBC has enough faith in "James" to hang onto it and attempt to bolster it. Top programmer Paul Klein says. "It's a terrific show and we're going to make it better.James is going to become 16. He's been a little naive. The intent was Holden Caulfield, but Holden Caulfield was not naive. The show is going to get a little harder."

A little harder? That sounds like car chases and laugh tracks. "I'm not sure what Paul means myself," says executive producer Dan Wakefield from his Hollywood office. "I'd put it a different way. I guess. We've been doing a lot of big 'issue' things, and what we're going to do is more real teen-age things, more like the teen-age subjects of the pilot - a love story, competition with the school jock, more about the school and James's life there."

Wakefield wrote the pilot and oversees scripts on all series episodes. He says that James will officially turn 16 on the Feb. 9 telecast, when the title will change, unsurprisingly enough, to "James at 16," Lance Kerwin, who plays James, recently celebrated his 17th birthday.

He still looks 14.

James has naturally had his amorous skirmishes with representatives of the opposite sex. Inevitable if not exactly burning question: Will James lose his virginity once he has turned 16?

"That's what is being planned," says Wakefield. "I can't say definitely 'if' and 'when', but I thimk it would be a good thing for us to deal with."

Since it is widely accepted that ABC won the ratings race by capturing the kid audience, and since "Happy Days" is the backbone of that particular conspiracy, you don't have is be too skeptical about TV to wonder if the new direction for "James" will be toward the proven and audience-strokin "Happy Days" formula Wakefiled says not to worry.

"It's not going to happen," he says. "We are not interested in doing that, nor capable of doing that if we were. It takes a particular kind of talent that I don't disparage but don't have either."

If there is occasional uncertainty in Kerwin's performance over the weeks, it's a charismatic kind of uncertainty, an involving kind, and it's anything but contrary to the nature of the character. Also, Kerwin has learned to use his expressive eyebrows with the cunning of a seasoned pr.

Perry Lang plays the fatally ill Bobby Graham. Lang seems to be specializing in distressed youths: this season he played the retarded Hewitt on "Hewitt's Just Different," an ABC Afterschool Special, and, more recently, the emotionally disturbed Buddy Bonkers on "The Fitzpatricks." It not the kind of typecasting that should be encouraged, but there's nothing to complain about in the way Lang handles his character tonight.

As always, there are certain pat or trite moments in the show, sometimes because of necessary narrative compression; but "James at 15" makes up for these by hitting highs of truthfulness most other shows don't even shoot for.

Every time a good program is canceled it's another little indictment of the commercial broadcasting system. The viewing public is a part of the system. It has to share the guilt. If we were to lose "James at 15," we would be losing more than "James at 15." There has to be room on television for shows like this.