EVER SINCE HE TOOK office, D.C. School Superintendent Vincent E. Reed has been getting high marks on his performance -- and deservedly so. But on Wednesday morning, he flunked a big test: With the assistance of the school board president, Minnie S. Woodson, and some bad guesses on the weather, Mr. Reed succeeded in simultaneously annoying tens of thousands of parents and elating their offspring by canceling all classes at the last minute. Until about 8:50 a.m. it had been the children who were annoyed -- for the official word had been "Go." And gone they mostly were by the time local radio and television stations could relay the later bulletin from Mr. Reed's office.

Now, regardless of whether you think the schools could or should have been open, school officials shouldn't change the marching orders the way they did, for it is more than just a matter of inconvenience -- it is dangerous. Children of all ages, having braved the weather and hazardous driving conditions to get to school, had to turn around and somehow find their way home. By that time, many parents -- having packed the requisite number of lunches and then driven, walked or waved their children off to school -- themselves had left for work, errands or what-have-you.

We do sympathize with Mr. Reed's strong desire to keep the schools open whenever possible. As he noted, "Our kids need all the time they can get in the classroom. Look at our test scores...." Besides, the public schools in the city are important in other ways, as places where many children from poor families are fed breakfast and lunch and are cared for; city schools feed free breakfasts to 19,000 children and free lunches to 49,000. And in most instances, principals in the elementary schools did their best on Wednesday to accommodate stranded children until they could be taken in somewhere else.

One of the biggest obstacles to keeping the D.C. schools open, however, is the number of teachers who live in the suburbs and who don't show up -- particularly when they've already heard that their counterparts in the suburbs have the day off. It is risky to have an entire building full of children and only a skeleton staff to supervise them. While taking that into consideration, school officials should make up their minds by 7 a.m. and stick with the decision.