One day last October, teacher Dorothy Porter was leading her second-grade class at Bruce-Monroe Elementary School to the lunchroom. She stopped and asked a tiny boy with two missing front teeth to stay behind a few minutes and finish a short assignment before he came down for lunch.

About an hour later, when all the other children were straggling back from lunch, the teary-eyed boy was still sitting there. He'd finished his assignment but hadn't dared move from the classroom without the teacher's express permission.

That's the way he was last October. The smallest of all the boys in his class, always afraid to speak up, he was in Mrs. Porter's "slow group" of students. They were still struggling to subtract 5 from 10 when the rest of the class was subtracting, say, 29 from 55.

He was among five of 27 pupils in Porter's class and among about 10,000 youngsters citywide who failed to master enough reading and mathematics skills last January to be promoted from grade 2A to 2B under the school system's new stiffer plan for promotions.

But after being held back one semester, the boy now can add and subtract two three-digit numbers, identify the possessive form of nouns, distinguish cause and effect in sentences and write numbers to 1,000 like other students working at second-grade level. And the boy has changed in another, more subtle way, too.

To his teacher ad others, he seems like a different child. He has broken out of his cocoon of shyness and blossomed into one of the most enthusiastic students in the class. Now, the once taciturn and fearful boy begs to be in charge of the class when Porter leaves the room. He isn't afraid to sit close to Porter anymore. Instead, he cheerfully completes his assignments, competing to be the first one finished in the class and go get everything right.

"I like school now," the boy explained through his two missing front teeth. "It's easy."

For the four other students in Porter's class who failed last semester, however, progress has been less dramatic. And right now, it is uncertain whether even the boy's improvement will be permanent. What happened to these children shows the wide range of results that the city's back-to-basics program has had on individual students.

Porter said the pupil progress plan, instituted in grades one to three last fall, has also been helpful for the brighter students as well, because it lets them move ahead at their own rate. For example, the second graders who can do third grade work are able to move ahead before the rest of the class.

Under the pupil progress plan, students are required each semester to master a certain number of skills in reading and mathematics, such as identifying homonyms, which are words that sound the same but have a different meaning and usually a different spelling, and counting by fives.

The system was aimed at halting the previous widespread practice of promoting students more on the basis of their age and the fact that it was the end of the school year, than on achievement. It also was aimed at eliminating cases of students graduating from high school without being able to read and compute. The number of students citywide who passed or failed under the pupil progress plan this semester should be known this week.

The plan seemed as likely to succeed at Bruce-Monroe as at any city school.

Last year Bruce-Monroe's third-and sixth-graders tested well below their grade level in reading; they were about a half-year behind in math. The student body is almost entirely black.

Many of the youngsters live in the large, brick, two-story houses of the Northwest Columbia Heights neighborhood, where the school is located.Their parents often work at unskilled jobs, although some are connected with nearby Howard University. About 30 percent of the families are on welfare, school officials said.

Students who failed the first semester, like the small boy, have gotten additional help from special reading and math teachers this semester. Many have also received tutoring twice a week since March from volunteers.

In the boy's case, his mother and older sister began helping him with his homework assignments. Porter scheduled the boy and her four other failing students for special attention during lessons.

"If there is good communication between the teacher, the child and the home, you are going to see a difference," said Porter, a soft-spoken, 25-year teaching veteran who treats her students in a gentle, motherly fashion.

All five students who failed in January were working below first-grade level when they entered second grade. Now all except one have shown they can do some second-grade, second-semester work, like forming compound words, finding the main idea of a story and measuring in inches.

Still, Porter is reluctant to pass them on to third grade in June.

"I can push them on to [grade] 3A, but it may be just frustrating for them," Porter said. "They are doing some of the same work as the other children who are on grade level, but the volume of work is not he same. Their rate of speed is slower."

Not all the students have improved as quickly as the boy, however. One Student, Stephen, has shown Porter he can do second grade work -- but only when he wants to. Then there is Gina, who is still almost a full year behind.

Though Gina will be staying in second grade next September, she will not have to repeat the same work, as was the practice in the past. Rather, her teacher will have Gina build on what she has already learned.

In almost all the cases where children have improved, their parents began taking a shaper interest in their children's schoolwork and helped and encouraged them at home, Porter said. But the effects of that cannot be measured easily.

"I definitely believe that if the children have problems at home," Porter said, "it does have a bearing on how they react in school." Take the case of Jennifer.

Like the boy, Jennifer was also failing during the first semester. Then Porter began sending notes home to Jennifer's mother. She talked about Jennifer's poor classroom performance with the child's aunt, who sometimes came to pick her niece up at school. She sent an attendance officer to the home to check on Jennifer's frequent absences.

Jennifer's attendance improved after the attendance officer's visit to the point where she was only absent three times in December and January, although Jennifer's attendance has dropped off since then.Her mother was often working nights the first semester and leaving for work just as Jennifer got home from school. Now, she has changed her schedule to be home in the evenings.

Sh does arithmetic and reading exercises with Jennifer almost every evening.

In October, Jennifer, one of the smallest, but one of the most articulate youngsters in the class (she would often mimic TV commercials and talk in adult terms about her neighbors and relatives), was still having difficulty sounding out her vowel sounds when other students in the class were reading paragraphs and writing their own sentences. She was still making mistakes in simple addition problems, such as 7 plus 2.

The other day, Jennifer swished back her braids and begged a reporter to listen to her read aloud a long, fairly difficult passage.

"When somone is speaking, we listen politely," she said, stumbling over the work "politely," but attempting to sound out the letters. Sometimes she mistook a work like when for where. But basically, she did fine. Porter said later that many of the words on the poster were ones learned in third grade.

Porter has noticed that, like the boy, as Jennifer's work improved, she became more friendly with the brightest pupils in the class. She used to stay mostly with the other children in the slow group.

In short, Porter said she thinks the pupil progress plan is "the best thing that I've seen happen in the system" because it tells teachers precisely what they should teach, allows students to move at their own pace and prevents those students who are falling behind from through the cracks into an education abyss. She said she believes the high rate of failures in the first semester will eventually be reduced as students become more accustomed to the new standards.

"It's much better to catch them while they are young," Porter said, than to keep promoting pupils when they have not learned the work.