In a rundown neighborhood in Anacostia where apartment windows are often barred and yards have been trampled bare, there is a Catholic elementary school where dozens of rose bushes grow outside the front door. Both the roses and the school are thriving.

For the 517 students - all but three of them black - who attend Our Lady of Perpetual Help Elementary, there is homework every night - even for children in kindergarten. There are required uniforms with blue ties for boys and plaid jumpers for girls. There are prayers that must be recited at least three times a day, even though 42 per cent of the students are Protestants.

Most of the teachers are strict. After school, students take turns sweeping classroom floors. Occasionally, there is a spanking if a youngster strays too far out of line.

But very few of the students at Our Lady of Perpetual Help miss their classes. Absenteeism at the school, which runs from kindergarten to eight grade, averages only about 3 per cent a day - compared to 8 per cent absenteeism in Washington's public elementary schools and 18 per cent in the public junior highs.

Most importantly, academic achievements at Our Lady of Perpetual Help is much higher than in Washington's public schools. Its students can read, according to standardized tests, at nearly the national standards for their grade levels, a relative rarity here.

The school's average achievement levels are still not as high as the principal. Sister Loretta Rosendale would like them to be. Most of the school's grades are about a half year below national norms.

But in the eighth grade, for example, the students at Our Lady of Perpetual Help average only seven months below the national norm in reading. Eighth graders in D.C. public schools average 2 1/2 years below the norm, and those in Anacostia scored even lower last year.

"Sometimes when we look at the test results, we get discouraged," Sister Loretta said. "In Montgomery Country, you know, they're a year or more above the norms and we want ours to be the best. But I think we can pat ourselves on the back a little when we compare ourselves with D.C., which is where most of our students live (Above 15 per cent come from Prince George's County.) When our students go on to high school, they're prepared."

"I guess we have a reputation of being a traditionaI school," Sister Loretta continued. "I don't know exactly what a traditional school is, or whether I should be complimented or not . . . We do expect the students to work here and some things - like spelling words - the teachers just pound into them."

One Anacostia parent, Dorothy Nelson, whose son Wayne entered seventh grade at Our Lady of Perpetual Help this fall, said his grades are lower now than they used to be in public scool. "But he doesn't mind going to school any more," she said. "There are no discipline problems, no bullies, and a lot more homework - about two hours a night."

"The kids are nicer here," said 12-year-old Wayne, who used to attend Moten ElementaSchool, which is across the street from Our Lady of Perpetual Help's upper school building on Morris Road SE. "They don't bully you or anything. Most of them do their homework."

But Sister Loretta stresses that Our Lady of Perpetual Help is "not just for the good kids."

"Sure we get kids who are scared of public school," she said. "But we also get some who are not achieving there and causing problems. It may not be the fault of the school or of the parents, but just that the kid needs change.

"Here they have to behave reasonably," she continued. "And we just don't have major problems. There's an atmosphere that's pounded into their heads . . . If they can't do it (remain well behaved), then we just have to tell the parents that Catholic school is not for everbody, and ask them to leave. That happens very rarely, but (the threat of explusion) is there.

The school gives placement tests to youngsters applying after first grade, Sister Loretta said, and turns down those who score far below students already enrolled. But there are "no hard and fast cutoffpoints," she said, and sometimes lowscoring applicants are admitted if they seem well motivated.

Within two buildings - one for kindergarten through fourth grade, the other for fifth through eigth - Our Lady of Pertpeutal Help is now the largest Catholic elementary school in Washington.

There are 24 others in the city plus 12 Catholic high schools, with an overall enrollment this year 12,120 students. The total is down just 59 students from a year ago - about one-half of 1 per cent - compared to a 4.7 per cent enrollment decline this fall in the city's public school.

Since 1965, the number of students attending Catholic schools in both Washington and its suburbs has dropped by about a third, which is roughly the same as Catholic school enrollment trends nationwide. Over the past four years, however, the rate of decline has been rather slight, and the Catholic schools here have, particularly those in the city have attracted substantial numbers of Prostesants, most of them black.

This fall non-Catholics made up 35 per cent of the enrollment in Washington's catholic elementary schools, compared to 21 per cent jsut four years ago and less than 5 per cent in 1965. In the Maryland suburbs which are also part of the Washington archdiocese, non-Catholic comprise 9 per cent of the Catholic students this fall, compared to just 2 per cent in 1973.

"The situation in our (Catholic) schools has stabilized," said Leonard De Flore, the superintendent of schools for the Washington archdiocese, "and non-Catholic have bcome an important factor. It used to be that the idea of having many non-Catholics in the Catholic schools just wasn't a possibility. The Catholic Church didn't think about it. The parents didn't think about it. But now it exists in every metropolitan area, particularly among blacks. I always see it as a great compliment that (nonCatholics) are weilling to send their children to Catholic schools."

All Catholic schools give preference to Catholics in admissions, De Flore said, and all children attending Catholic schools, no matter what their faith, must take the same Catholic religion classes daily and attend mass, although Protestants do not take communion.

Every year, Our Lady of Perpetual Help School produces a trickle of converts - families as well as children, said the Rev. Peter J. Kenney, the priest at Our Lady of Perpetual Help Church who has general authority over the school. But he explained: "We don't look at the school necessarily as an agency of proselytizing . . . But we do want to expose people to a system of Christian values. We believe you can't compartmentalize religion nad say it is just something you confine to 20 minutes a day."

Lillian Carter, who is a Methodist, has two children in the school for the past seven years.

"At first it was very hard for me to explain to them about not being Catholic," she said. "They wanted to be confirmed in second grade like everyone else. I told them to wait until they turned 12 and then they could make up their own minds. . . . Now they've become very active in the Protestant church, and there's no pressure on them at the school to become Catholic."

Father Kenney said he is worried by the increase in the school's tuition, up by $100 a child in the past two years. The rate now is $330 a year for parish members, whose education is subsidized by other church income, and $505 for nonmembers, who pay full cost. There are discounts for families with more than one child in the school.

The charge for parishioners is about average for Catholic elementary schools in the city, but about 25 per cent more than average fees in suburban Catholic schools, whose parishes can afford bigger subsidies.

The tuition still is much less, however, than in non-Catholic private schools, where charges often exceed $2,000 a year. "We don't want to become an elite school," Father Kenney said. "But with costs ascending we are screening out low-income people."

Even so, slightly more than half of the childen at the school are eligible for federal aid given to youngsters from poor families. About 15 per cent of the students, Father Kenney said, come from families on welfare. They also pay tuition, he said, but at a reduced rate of $15 to $25 a month. They are also expected to contribute personal service to the parish.

"I sacrifice. Believe me I do," said Victoria Davis, who lives in the Barry Farms public housing project and sends two sons to Our Lady of Perpetual Help. Mrs. Davis said she pays $25 a month for tuition out of $365 in income from welfare and child support. She said she works regularly as a volunteer in the church kitchen.

"The school is worth every penny I pay for it and all the time I spend too," she said."You have to be willing to forfeit some of what you have to help your children

"It's a very bad neighborhood out here, and when your children go to public school they're in the same environment. I send mine to Catholic school because I want them to get out of it even though I can't."

Inside the school's 68year old building at 1409 V Street SE, most of the rooms, which house kindergarten through fourth grade, have curtains on the windows, rocking chairs for teachers, and carpets in a corner for children to sprawl on. Last week they were decorated profusely for Christmas.

"The parents and the priests do all the painting and repairing," said Sister Jane Burke, the principal of the lower school. "They really work at trying to make it something nice."

The upper grade school, built 20 years ago, is located next to Our Lady of Perpetual Help Church, a circular modern building, on 16 acres on a hill that is the second highest point in Washington, with a sweeping view of the capital's major buildings and monuments.

In both school buildings classes range from 28 to 38 students, far smaller than they were a decade ago when they sometimes reached 45, but considerably larger than the average class size of 25 in D.C. public schools.

Compared to the public schools, teachers' salaries are low - only $4,325 a year for the six nuns and no more than $11,000 a year for the 11 lay teachers. Teacher's salaries in the D.C. public schools range from $11,824 a year up to about $23,000.

"It's been pretty special teaching here," said Lucinda Jasper, a sixth grade teacher. "The pay has been low, but we don't have the problems the public schools have. We can spend our time on teaching."

Nuns and lay teachers now dress alike, except for one, Sister Kenneth Marie, who still wears a veil. Several of the parents interviewed for this article said they wished the nuns had stayed in their habits. All of then said they where glad their children had to come to school in uniform even though many of the older students said they don't like wearing the same clothes every day.

"The uniforms make all the children equal no matter what their parents earn," said Benjamin Contee, the PTA president. "All in all, I think they're slightly cheaper than having to buy different clothes . . . The children can be individuals even when they're in uniform.""

The school's policy of occasionally spanking children who misbehave also seems to have parental suppor

"I want my son to go to Catholic school because he'll get discipline there," said Beverly Lucas. "They're not afraid to spank your child, and I say, 'Yes, if a child is bad innclass, then you spank him.' But it's no way as strict as it used to be."

Supt. De Flore said the Catholic school board has a policy against colporal punishment. "If there's a specific complaint," he said, "We investigate. But we have many other thinks to concern ourselves with."

Even though costs at Our Lady of Perpetual Help have risen to about $500 per pupil a year, they are still far less than the $2,000 a year per pupil cost in D.C. public schools.

Besides having relatively large classes, lowpaid teachers, and low maintenance costs, the school keeps costs down by cutting back on what Father Kenney calls frills. Unlike public schools, Our Lady of Perpetual Help has no nonprofessional aides - parents volunteer instead. There are no special teachers for art, music, or physical education; these subjects are taught by regular classroom teacher. For children in the upper school, physical education classes are held in a park, except in bad weather when they switch to the church social hall.

The one thing the school doesn't skip on is books. EVery afternoon most children carry home big satchels of them to do their homework. By contrast, when children leave Moten, the public school across the streets, few take books with them.

"I like to see them taking all those books home," Dorotthy Nelson said. "That's the way a school ought to be."