Those who resent intrusions on the cockles of their hearts will probably spurn the advances made by "A Circle of Children," a two-hour CBS drama special at 9 o'clock tonight on Channel 9. But for many viewers, the emotional manipulation will prove both pleasureable and satisfying.

This is another of TV's sensitivity sessions, a fact-derived fiction designed to make us feel warm, hopeful, encouraged and safe. Such stories are always about either people with terminal diseases or disturbed youngsters. The youngsters in "Children" are not so disturbed that they aren't also adorable, heart-tugging and photogenic.

If the script, by producer Steven Gethers, never stretchers an inch beyond adequacy, two performers manage to elevate the project well beyond its perfunctory aims: Jane Alexander as Mary MacCracken, the too-affluent suburban divorcee looking for a time-killing cause, and Rachel Roberts as Helga, a German-born teacher with an instinctual affinity for the socially handicapped and the disenfranchised.

Helga rules the roost at a small school for austitic, schizophrenic, and emotionally disturbed children, and MacCracken is her new earnest if naive volunteer aide. At first, Helga comes on like a commandante ("You vill pleez to sharpen zee pencils"), but as the story progresses, both actresses illuminate and develop their roles with really remarkable effectiveness. One leaves the story with enormous respect for them both.

Gether's script, competently directed by TV veteran Don Taylor, is based on the 1973 book "A Circle of Children" by the real-life Mary MacCracken. The book was not precisely real-life, however; MacCracken chose to write a novel rather than a nonfiction account of her work as a volunteer, stating in a preface that, "this book recounts the essence of my experience and in that sense is a true story."

Naturally we get at least one giant step further from the truth with the TV version. Characters have been scaled down or eliminated, and the problems, besetting the children have been carefully tidied up for the TV audience. There is, for instance, no sign of the little girl who spent most of her waking hours drawing pictures of women's breast, nor of the child given to lengthy and guideless orations of obscenities.

One of MacCracken's own children has been written out, and so has Helga's husband, obviously to make Helga a still more sympathetic, perhaps pathetic, figure. You can't blame Gether for such ploys, though, because that one facilitates a weepy "good-bye, Helga" scene that harkens back to such classically emotional movie farewell as Ingrid Bergman's departure in "The Bells of St. Mary's" and, of course, the immortally arduous ta-ta of dear old Mr. Chips.

Indeed, throughout "A Cirle of Children," Getcher is repeatedly guilty of coarse dramatic devices that are deplorable only if they don't work, and it happens that most of them do. Even the implausibly pat ways in which some of the children's problems are resolved can be accepted in this context, partly because the beautifully harmonized performances of Alexander and Roberts help sustain credibility against all odds.

David Ogden Stiers, as Dan, another teacher, also contributes to the integrity of the story, but nothing whatever is added by Nelson Riddle's achingly trite and predictable score which has the bad taste to culminate in a ridiculously misconceived title tune beneath the closing credits. Indeed, some of the elements of "A Circle of Children" are such TV-movie prerequisites that they make you want to scream right along with the kids.

Gethers punched up the conflict between MacCracken and Helga - which is not nearly so strident in the book but at least he has the decency to resolve it fairly early in the story and get on to more susbtantial matters. The MacCracken character's greatest conquest is with a boy called Brian who seems unable to talk and whose greatest affliction may be an addiction to television. When Brian's problem is overcome - in a truly unbelievable manner - the story nevertheless reaches the kind of shameless emotional high that is lamentably rare on television.