With "The Late Great Me: Story of a Teenage Alcoholic," the ABC Afterschool Special bites off more than usual but not more than it can chew. The program expands to 90 minutes for the first time today to tell the lesson-laden tale of an adolescent drunk, at 4 on Channel 7.

Based on a novel by Sandra Scoppettone, "Me" chronicles the trip and fall of a 15-year-old named Geri, who starts drinking with her boyfriend because it makes problems of adjustment and acceptance go poof. A pattern of casual lying turns into a life of deception until a crisis forces the girl to admit that she is very ill.

Jan Hartman's script manages, in that usual spirit of this series, to turn message-delivery into a genuine story about people. But Maia Danziger, who plays Geri, is a twitchily affected young actress whose lips make hoops when she talks, somewhat lessening the fervor with which a viewer might pull for her.

Still, the film, directed by Tony Lover and produced by Daniel Wilson's company, establishes a new beachhead of tough-mindedness and realism for the Afterschool Specials, which have been earning ABC deserved hoorays for seven years. At the end of today's program, Danziger will tell viewers concerned about alcoholism to contact the National Council on Alcoholism or Alcoholics Anonymous. At the end of "All Quiet on the Western Front," Richard Thomas will step out of character to recommend a reading list of related books.

Whatever would we do without television networks?