Everyday heroism remains one of the most appealing subjects for the TV movie. In "Evil in Clear River," the ABC film at 9 tonight on Channel 7, Lindsay Wagner plays a mother in a small town who fights a lonely but victorious battle against a bigot who is teaching anti-Semitism to his high school history students.

ABC terms the film "a fictionalized drama suggested by real events." It is set in what one character refers to as "a sleepy little farm town" in snowy Alberta. As Kate McKinnon, Wagner wakes the town up to a man who is poisoning the minds of its children with his deranged view of 20th-century history.

Written by William Schmidt and directed by Karen Arthur, "Clear River" is one of those admirable television primitives-basic, schematic, almost ritualistic, yet in its uncluttered way stirring and satisfying. For standing up to the racist, who is also the town's mayor and immensely popular with the citizenry, Kate is ostracized by neighbors and bitterly resented by her son, who has come to idolize the teacher.

Randy Quaid, so ferociously memorable last year as Lyndon Johnson in the NBC movie "LBJ: The Early Years," gives a much less bombastic but no less effective performance here as Pete Suvak, beneath whose affable grin and folksy demeanor lies a venomous philosophy: "The Jews" are in league with the Devil, they have embarked on a plan for world domination, the Holocaust never really happened, and Hitler was a victim of bad public relations.

Is it credible that a man could be teaching this kind of thing to succeeding classes of high school students with no one, until gallant Kate, raising a protest? Clear River is an isolated town with no minorities visible among its population. And it's made clear that Suvak's personal popularity has made it possible for what are called his "little theories" to be patiently tolerated.

So, yes, the film does offer a convincing case that something like this could occur. God knows there's never a shortage of spiteful lunatics in the world.

Wagner shows new depth and maturity in the role of Kate. She never seems to be stretching; it fits her remarkably well, and she and Quaid make formidable adversaries.

There is one miscalculation. So that she wouldn't seem a saint, the writer gave her a flaw: Kate smokes. Everywhere. Even in a barn full of hay and straw. Couldn't she have, say, cracked her knuckles instead?

Thomas Wilson Brown, as McKinnon's perplexed son Mark, and Michael Flynn as her husband contribute solid support. Ironically, with so many TV shows and movies set in the United States now being shot in Canada, this film set in Canada was shot near Salt Lake City.