Sex bias in training children obviously isn't limited to the classroom. Psychologists have shown it begins as early as birth in the inflection of a parent's voice and in the manner of handling infants.

Parents can try to modify sex stereotyping, say researchers Myra and David Sadker, by watching their own behavior and by neutralizing the outside influences which they can't eliminate, short of isolating their children at home. Parents, they say, need to be more affirmative in combating sex stereotyping just as they encourage good manners and discourage racial and religious prejudice.

Among their suggestions:

* Make sure both parents join in helping children with their homework. Studies show that after the third grade, students take their math problems to Dad.

* Don't accept such stereotypes as girls are not as adept as boys in spatial ability. Allow girls freedom at an early age to explore their surroundings and to play with building materials.

* Open a full spectrum of careers to both sexes. Studies show that by the fourth grade, boys can identify numerous careers while girls limit themselves to very few.

* Don't give in solely to your child's choice of toys. If a daughter requests a Barbie doll, you might also give her a chemistry set--and show her how to use it.

* Try to evaluate the extent of sex discrimination in your child's school. At the high-school level, clues include the number of girls enrolled in advanced math classes (math and science classes are seen as the gateway to certain traditionally male careers). At the college level, look at the male/female ratio of the teaching and administrative staffs.