THE COTTON plaid dress and new white knee socks are already laid out, and for weeks I've been trying to cram some last- minute mental reinforcement into my daughter before sending her off to first grade dressed in this traditional back-to-school outfit on Tuesday morning.

Surely, the lump in my throat and the anxious clutching round the heart area are not unlike pangs other parents across the land are experiencing as they get ready for the post-Labor Day partings that mark a milestone on their children's way to growing up.

In some ways my jitters are very like those my desk mate, Jo-Ann, is having for her first-grader, Jessica, who is "so little, and wears glasses and just seems so vulnerable," going from day care into her first institutional experience and to a school with bigger children.

But my worries and wistfulness come from a different source. After all, I have put my daughter, Destiny, who's almost 6, on a school bus every September for four years. She has cerebral palsy and has been in one special-education program after another since she was 2.

This year, however, will be her first in a "regular" classroom. Though she returns to the public school where she attended kindergarten last year, she will be mainstreamed. That means being outnumbered by able-bodied children for the first time. It means a departure from the cocoon of special classrooms where the children were few and each had some handicap and a distinctive way of being delightful in spite of it, or because of it.

Destiny's own disability is on the mild end of the wide range of disorders caused by brain damage that are labeled cerebral palsy. Hers is mainly rooted in spasticity -- failure of sets of muscles to contract and relax normally. The result is clumsiness and lack of balance.

Born two months prematurely, she weighed less than four pounds and her lungs were inadequately developed. She sat up at 18 months, began crawling at age 2 and now walks, though only with the support of a walker, and in an awkward, hesitant manner. Fortunately, she escaped the learning disability that usually accompanies her condition as well as the usual speech impairment, and in fact, started talking early and developed vocabulary and verbal skills well beyond her age level.

Until now, she has been only one special child among many. But come Tuesday, she crosses the threshold into a microcosm of the non-handicapped world she'll have to contend with for the rest of her life.

She's a little apprehensive. I'm terrified.

It's not because of the curiosity, insensitivity and cruelty she'll surely encounter. Those are predictable in a biased and ignorant world. Rather it is my fear of having inadequately prepared her to face down those reactions from an able-bodied society where even the well-intentioned are likely to talk down to her -- and probably look down on her -- as though her intelligence somehow is impaired by the lack of coordination in her limbs.

Already I've felt the icy sting from an admired and intelligent friend's account of how "cute" it was to see her little nephew recognize a wheelchair symbol on a public elevator and announce, "That's for crippled people."

And maybe I did overreact last Christmas, as relatives said, when I eavesdropped on Destiny and two cousins playing school and heard the child playing teacher order her to "get over in that corner. It's for people who can't walk." (I still don't know whether it hurt more to hear the command or to see her crawling off to obey it.)

But, being black and female, and having already felt a couple of lifetimes worth of anger over the assigning of people to one corner or another because of their sex or race, I admittedly lack the tolerance to make light of insensitivity, even from innocents, even from family.

On the other hand, I know the need for caution. I'd rather send my "crippled kid" into such a world with her face turned to the sun. I know that I can neither shield her from, nor absorb for her, the hurts she'll face because of her sex, race and physical handicap. And I know intellectually that she will have a better chance of attracting the better side of people if she is armed with a countenance and bearing that signify she expects nothing less, rather than a defensive or defiant posture.

And that's the point where I worry whether my excessive parental concern becomes a liability. After all it's my handicap that emotionally I still react to my sturdy, loquacious, charming, often brave and sometimes arrogant child as though she were still a helpless 3 1/2-pound infant.

But my problem doesn't end there. I am saddled with an ambivalence. I don't want the world to see in my daughter only her disability -- any more than I want the world to see in me only my blackness. She is more than capable of doing many things and many things for herself. But, at the same time, just as I want my own specialness acknowledged and appreciated, I am aware that my daughter cannot do everything that other children can do.

So, having imbued this impending first day of first grade with so much significance, my task between now and Tuesday is to make sure I haven't weighed down my little girl with too much of my own apprehension -- to somehow recognize the seriousness of the occasion without exaggerating it.

And, on reflection, that's probably not very different from the challenge faced by responsible mothers and fathers of first graders everywhere.