A rubble-strewn lot, long a neighborhood eyesore and hangout for local youth gangs, is cleaned up and landscaped.
As a result, ''if anybody is fighting, they can't pick up a can and throw it at someone,'' said Maureen, a fifth grader at Public School 7 in the Bronx.
Obviously, there's nothing unusual about children cleaning up a vacant lot. But the cleanup by Maureen and other schoolchildren of Public School 7 is part of a major new effort by schools citywide to teach the principles of responsible citizenship.
In an effort to check an unrelenting juvenile crime problem in New York City schools, school officials this fall launched an experimental class in old-fashioned ethics. The hope is that students will emerge from the program with a greater ''concern for the life, well-being, and dignity of others,'' said Charlotte Frank, curriculum chief for the Board of Education.
While individual teachers in schools across the country may have labored to instill in their students a basic respect for law and the well-being of classmates, the nation's largest city is believed to be the first to teach ethics on a systemwide scale.
Some juvenile crime experts are pleased to find New York City schoolteachers discussing the elements of good citizenship with their students. But many teachers and principals closest to the project are little more than cautiously optimistic about what practical impact, if any, the program may have on reducing school-related crime, not to mention offenses by juveniles off campus.
During the 1981-82 school year, more than 15,615 crimes - ranging from serious assaults and weapons offenses to vandalism - were reported in the 1,000 public schools, according to the New York City Board of Education.
To curtail school crime, the city hired hundreds of security guards and installed closed-circuit television in the most crime-ridden schools. Most juvenile crimes, however, are committed outside the school grounds, and the city's jails and juvenile detention centers are crowded with youths awaiting trial or transfer to institutions upstate.
But the clamoring over juvenile crime is only one contributor to the creation of a good citizenship program. For another, public perception of school administrators has soured in recent years, and people such as Mrs. Frank have been bombarded by complaints that they were not doing their share to prepare children to become responsible, law-abiding citizens.
Then, demands on schools to do something intensified when New York City experienced vast cuts in federally sponsored social services outside the schools. Currently, ''the main human-services institution for youngsters is the school,'' says Chancellor Frank J. Macchiarola, who helped spearhead the citizenship program.
While school officials say it is ''too early to tell'' what effect the program will have on crime statistics, teachers and visitors are impressed that some students already seem to be changing their attitudes about littering, vandalism, and other antisocial behavior.
The good-citizenship classes take different forms at different schools. At Public School 7, for example, teacher Richard Rubin has been assigned as the full-time citizenship teacher.
''I'm the citizenship teacher,'' proudly proclaims Mr. Rubin, who has been teaching for 16 years. ''You generally have a science teacher, a math teacher, an English teacher, a gym teacher. But it's very unusual to be a teacher in citizenship.''
Rubin meets with 20 different classes a week, and the academic exercises in citizenship are sometimes ''acted out'' as well as discussed. At one of his classes, Rubin dumped a wastepaper basket full of crumpled paper onto the floor to ask students how trash affects others in the room.
All the students agreed that throwing paper on the floor was the wrong thing to do. The more difficult question for these elementary school students came when Rubin asked them ''How this would affect others?''
''The garbage might fall behind someone else's desk and they would get the blame,'' a little girl with pigtails piped up.
Most other New York City schools have not assigned a teacher to teach only citizenship classes. Rather, most teachers, aided by a ''Citizenship in New York City'' manual, are setting aside a portion of each week to discuss real and hypothetical examples of problems.
The examples, teachers say, show ways the problems might have been avoided if people, adults as well as children, had displayed more concern for the welfare of others.