THE FIRST DAY of school has never been easy for me. It wasn't easy some 30 years ago when my very own mother abandoned me at Alta Vista Elementary School in Bethesda and I spent the entire day (it couldn't have been just one morning) weeping forlornly in a corner, sure that the afternoon bus would deposit me not at my own home which was gone forever, but in the Baptist orphanage. On my childhood terror index, the first day of school compared only to the time my parents abandoned me in a strange Sunday school class with a cold and no hankie.

These are not, as you may have guessed, experiences one forgets, particularly since, in my case, they came right about the time I became secretly convinced I had been adopted. Why else were my parents' friends forever taking hard looks at me and announcing with a shake of the head that I didn't look a bit like anyone else in the family.

We call all these feelings separation anxiety now, and I don't know what we called them then, but whatever we labeled it, I had it in spades. I resolved years ago, that my children would get a better deal on the first day of school than I had. No separation anxiety for them.

The first child who went off to nursery school some 10 years ago did just fine. We spent a week chatting up this terrific adventure he was in for. The first day after Labor Day we drove him to school and watched him hop out of the car and bound into the school building with not much more than a backward wave and a smile. By the time he got home at noon, I had recovered. It seems that no one had bothered to warn me that the first day of school, even if it's nursery school, is the first step away from home, the first step of a series of wrenching steps toward independence that parents are forever saying they can't wait to have happen and can't bear to have happen when they do.

But I survived. Having wept once as an abandoned child and once as a clinging mother, I had obviously suffered both sides of separation anxiety on the first day of school. These are the kinds of experiences that make a mother out of you, and I knew for sure that I wouldn't have the same kind of reactions when the younger children went off.

Not me. After all, I was by now a full-fledged certified mother who works outside the home and all the studies show that these kinds of mothers don't have clinging children, if for no other reason that these mothers aren't around to cling to. The studies also show that these mothers tend to have outgoing children, presumably since these children go out to day-care centers and baby sitters and have to speak for themselves.

The first day of kindergarten dawned blue and hot yesterday and it never occurred to me that there would be any problem. I was, by now, an experienced mother. The resident 4-year-old was, by now, an outgoing child who had, after all, 1 1/2 years of preschool credits, not to mention hundreds of hours in a neighborhood play group. And hadn't he been talking about his new school all summer?

The first clue had come late Monday when I was tucking him in for a nap and he looked me squarely in the eye and announced he wished he could go back to his old school. I chalked that up to natural apprehension and there's nothing wrong with kids having a little old-fashioned apprehension nowadays. Well, he was either tired enough or apprehensive enough that he continued his nap on through the night and didn't show up again until 7:15 yesterday morning, when he arrived in the bedroom and announced that he was ready to go to school.

By 10 of nine, so was I. So, it turned out, was my husband who announced he wasn't going to miss the child's first day of school. On the way, we went over the names of his teachers, the number of his classroom and his bus. Through it all, my 4-year-old boulevardier, who had traveled up and down the East Coast this summer, who had braved the force of ocean waves and the depths of mountain lakes, was sitting tensely on my lap, not moving or talking, a condition that in 4-year-olds is usually symptomatic of impending carsickness or impending getting caught.

By the time we got out of the car, he was clutching my hand. He nodded to a few of his friends when we got into the school, but that was it. "He seemed a little quiet," one mother said later, "which is not," she added delicately, "like him."

The long walk down the hallway to the classroom was tense and the classroom was, of course, the very last one on the hallway. By the time we got there, his hand had fastened around mine like a vise, and the fact that four or five children were sitting around a desk, still alive, did not do much to relieve his anxiety. A teacher greeted him warmly, indicating she had seen him around the neighborhood pool. That seemed to help. She put a decorated name tag around his neck and I leaned over to kiss him goodbye.

And for that moment, the 4-year-old, who usually has all the answers, looked up with a question. He didn't run off into the classroom to explore. He didn't say a thing. Instead, he stood, chin up, very still and when I leaned over he gave me a very long kiss on the cheek and a very hard hug around the neck, and I think, when I stood up to go, that there was a tear in his eye, too.