"The Acorn People," tonight's NBC Monday Night at the Movies offering, presents a strange contradiction -- a movie best viewed by children, but aired at a time when most children should be in bed (9 to 11 p.m.).

The movie is about a summer camp for physically handicapped children. It is short on plot and long on social messages, all constructive. It is also just plain long, coming belatedly to a climax that is certainly heartwarming but not enough to justify the time it takes to get to it.

The main message is that handicapped children seem frightening but have the same concerns and mischievousness as normal kids. The film is also anti-mainstreaming -- the school of thought that holds that handicapped children are best served by being forced to adapt to the "regular" world, without special ramps, activities and so forth. The villain of this piece is the camp director, a former marine named Bradshaw, who is furious when the hero (Ted Bessell) tries to build ramps for the weelchairs, and shows the campers a water-sports film peopled, agonizingly, by children with perfect bodies.

With a little rebellion, egged on by the excessively cheery camp nurse played by Cloris Leachman, the campers and counselors defy the old meanie's orders for the last day at camp and stage a water ballet, capped by the valiant efforts of Bessell's charges to crawl, wheel, drag and otherwise heave themselves up a hill to plant a flag made of the camp director's undershots.

The children in the cast are clearly "real" handicapped kids, and the characters they create are charming and relatively unsentimental. Anyone who has been around handicapped kids can detect a good deal of reality in the way they interact.

Why, in their infinite wisdom, the network brains behind this film didn't shorten the script and show it at an hour when children, who could be positively influenced by "The Acorn People," could see it, is one of those mysteries networks delight in perpetuating.