Tens of thousands of District of Columbia youngsters had reported to their schools yesterday morning when officials made a last-minute decision to cancel classes because of snow.

After repeated assurances that schools would open on time, School Superintendent Vincent E. Reed and school board president Minnie S. Woodson, acting on a more accurate weather forecast they had just received. decided sometime after 8 a.m. to close the schools, throwing thousands of parents and children into a state of confusion.

Word of the closing was not broadcast over local radio and television stations until about 8:50 a.m., barely 10 minutes before school was to start. As a result, large numbers of students already had left for school, or arrived there, when they heard the news.

Some children promptly went home, while others in lower grades remained in auditoriums and cafeterias until their surprised and irritated parents, some of whom had gone to work, could fetch them.

"I was heading back home but I decided to call first," said Margaret Baker, a receptionist at the HUD building who had sent her child to school and then gone to work. "And lo and behold, my little fourth-grader was back home. He had used his lunch money to ride the bus. I was so proud, but if something had happened to him, I'll tell you now I would sue..."

After Reed and Woodson reached the decision to close schools, Reed said, he and several staff members called the Associated Press. United Press International and radio and television at 8:15 a.m.

However, Woodson recalled that she had a "prolonged conversation" with Reed after Reed spoke with weather forecasters about 8 a.m. Woodson said the decision to close schools was made about 8:30 a.m.

According to a spokeswoman for WTOP, an all-news radio station, school officials did not notify the station of the decision to close schools until 8:50 a.m.

Several other radio stations said they did not know exactly when the notification came from the school system but said the call came "around 9."

When Reed was asked how many students had arrived at school when the announcement reached them, he said: "... how many left and went home... I really don't know."

Reed said school officials estimate that 12,000 students remained in schools after the announcement.

"I imagine that when the word got out at 8:20, a lot of kids had left for school," Reed said.

Reed, saying "I've got mud on my face with this one," noted that on snow days the absenteeism rate is 9 percent for elementary schools, 8 percent for junior highs and 21 percent for high schools.

Many students arrive late on snow days, he said.

"I don't like to close schools." Reed said "Our kids need all the time they can get in the classroom. Look at our test scores. That's why we're working 12, 14 hours a day here and why we need all the time we can get in the classroom."

"This phone was ringing off the hook." Reed said yesterday afternoon from his 12th floor office overlooking a snow-covered Pennsylvania Avenue. "And I took every one of those calls. Those parents were angry before they had a chance to talk. Now don't misunderstand me, they were still angry after we talked but they felt better once they got an understanding of what had happened and didn't feel that some jerk was sitting down here being wishy-washy about this."

What happened, according to Reed, was that the forecast he received at about 6 a.m. from the highway and traffic division of the D.C. Department of Transportation called for "a warming trend that would bring rain by 2 o'clock and wash the snow away."

Reed said he felt the roads were sufficiently clear for most students to get to school and the rain would clear the streets and allow students to get home at 3 p.m.

But as the snow continued to fall heavily, Reed said he called the forecasters again. Their new, 8 a.m. forecast cast was that the snow would continue falling throughout the day without any "warming trend," Reed said, so he called school board president Woodson and they agreed to close the schools.

"Schools are a very important item in life and we didn't want to make a decision lightly about closing them," said Woodson. "... Some children are fed breakfast and lunch at school so we wanted to be very careful, occasonally you make a mistake and when it comes out in the papers you look like a dummy. But we're human."

"If we had listened to the radio," Woodson added, "we would have already closed schools three times this year. Some of the parents who called me said why didn't I look out the window. Well, at 6:30, when I looked out of my window, it was just barely snowing and looking out of the window I couldn't tell if it was snowing across town. That's not what you go by."

Reed said comparisons of the city school system to suburban school systems, whose closings were announced by 6 a.m. yesterday are unfair. He said suburban schools use buses to transport 80 percent of students while most city pupils walk. Like Woodson, Reed noted the breakfast and lunch programs. City schools feed 19,000 children free breakfast and 49,000 free lunch, he said.

Reed said some elementary schools remained open as late as noon despite the decision to close schools because students had to be cared for until their parents could be contacted and plans made for the child to spend the day somewhere.

"You had some angry people out there this morning," said Harold Fisher, assistant to the president of the Washington Teachers' Union. "Our phones were flooded with calls -- parents and teachers -- and I never heard them use the kind of language they used this morning to refer to Reed and the school system... Reed gave no consideration to the safety of kids. He must have heard those reports about cars slipping and slidding all over. He knows most of our kids walk to school and have to cross streets. He knows"

Reed said he did not know how many teachers reported to school yesterday and said his staff is tabulating the number of city teachers who live in the suburbs. All teachers are to be paid for yesterday, Reed said.

A random survey of elementary schools in the city showed that a very small number of teachers reported for duty yesterday morning, according to principals.

"Most of the kids heard the news before they were in here," said Evelyn Taylor of the Nichols Avenue Elementary School in Southeast Washington. "I could hear people in the street yelling that schools were closed before I knew it."

The reaction of children to the snowfall was predictably joyous. "We were having a science test today," said Joshua Jones, an 11-year-old student who was smiling with obvious relief as he sloshed his way home along Rhode Island Avenue NW.

The headache of the last-minute announcement anguished some parents.

Barbara Anderson of Southeast Washington was shifting between anger at the school system and concern for her children as she waited to find out what had happened to her two boys. Confident that schools would open, she had dressed them three layers deep in snow clothes and sent them to Sousa Junior High yesterday morning.

"I called home and no one answered," said Anderson who was at work when her husband phoned from his job to tell her schools were closed.

"I called the school, and they said the boys had been sent home an hour ago. Somewhere out in this city I had two nearly teen-age boys roaming around, and I didn't know what to do", she said.

Two hours later, the boys answered the phone at the Anderson home. They were fine, they told their mother.