NOT being the nostalgic type, my mother gleefully claims to have thrown out all her children's unclaimed treasures long ago. Something about living in the midst of our abandoned ski trophies and drying junior-prom bouquets set her on a mission to recapture the upstairs for guest quarters early on, before the last of us even had time to win our varsity letters and pin them to our bedroom walls.Despite her best efforts, however, I still trip over the occasional relic when I go home. Most recently it was a collection of school photos - the kind with surreal sunsets for backdrops that come in both the convenient wallet-size-by-the-dozen and suitable-for-framing three-by-fives. I found them stuffed in an envelope and oddly filed in a kitchen cabinet, behind the vanilla extract. What struck me when I found them, and strikes me still, is that these pictures hold no memories for me from my school days. Sure, they tell which dress was my favorite that year, and what the state of my pigtails was at the time of the photographer's annual visit. But for a real sense of my school days, skip the studio shot and give me one of my mother's first-day-of-school snapshots. They tell all. Take the first-day photograph from grade six, for example. I look at that picture and relive the daunting prospect of junior high. There would be new kids to meet for the first time since kindergarten, including crosstown legends Jane Watts and Leslie Goodnow. The boys back at North School had started talking about them during fifth-grade recesses. I was sure they'd be wearing nylons, complete with garter belts, and shoes that had heels. They probably even wore eye shadow. The prospect was unnerving. The anxieties come back to me when I look at the dress in the photo, all paisley and ric-rac, too cute for junior high, I was sure. The tights I had on were dark and itchy and much too thick for that Indian-summer day, but somehow less childish to my 11-year-old mind than knee socks. How was I to know that I would discover the joys of canteen, so much more mature than recess, and the marvels of study hall, in an auditorium with a real stage and heavy velvet curtains, before the first day was over? How could I imagine the relief I would feel that very afternoon when I met a south-side girl named Debbie Cowan, longer and lankier, and even more a tomboy than I was? And why does looking at that photo remind me of all that, and more? Then there's 11th grade. By then I assumed the look of a less anxious me, a more annoyed-with-mother's-silly-rituals me. My frayed white turtleneck and gauzy beaded top, both tucked into faded Levis, recall the days when even the first day of school was nothing to get dressed up for and certainly nothing to worry about. I look at the photo and remember finding my locker, alphabetically sandwiched between David Hoch's and Margaret Hodgkins's, right where I knew it would be. I remember knowing exactly who I'd see in my English class, where I'd sit during lunch, which field hockey stick would be mine. By the 11th grade, I knew the routine. Opening day held no surprises. Ah, for the perfect first day, where life was neither so predictable as late high school nor so daunting as early junior high. For perfection, give me kindergarten! Give me the smell of a new pinafore and matching blouse, picked a month before from the pages of the Sears Roebuck catalog. Give me the first taste of school paste, the first smell of purple mimeograph ink, the first box of school-issued crayons - as stubby as my own fingers. Give me the squeak of the seat cushions and the grinding of gears i n the big yellow bus - the first bus ride of my life. Just show me that picture, and make it all come back! It makes me wonder whether any of my momentous rites of passage - the blowing out of candles, the trip to the hospital to meet a new sibling, the opening of Christmas stockings - would be remembered half as well if my mother hadn't caught each milestone on film. What is it about those candid moments that makes me able to retrieve an entire day, these many years past? Would I still remember the taste of those maple-sugar Santas or the smell of burning jack-o'-lantern lids half as well without the photographs to remind me? Would the Tuesday after Labor Day always tingle like the first day of school if Mom hadn't pulled out the old brown Minolta and popped a new bulb in the flash attachment, prompting these sensory memories each year? THERE'S a school bus stop just outside my front door, where all the kids in my neighborhood will be swinging lunchboxes and comparing new footwear this morning. Two blocks away, a caravan of college freshmen will start pulling into campus, their parents' station wagons stuffed with stereo equipment and computer gear, and maybe even a precious high school relic or two that would've gotten pitched if it had been left back at my house. I think I'll go for a walk this morning and take my camera with me.