Stevens and Ross Elementary schools in downtown Washington had a new principal yesterday. She sat on tiny chairs to help 4-year-old students make cutouts, gave a pep talk to the schools' safety patrol officers, answered phones, and greeted first grade Hispanic students with "Buenos dias. Como estas?"

In fact, the new face at Stevens was no new face at all to city schools but that of Superintendent Floretta D. McKenzie, who switched roles for a day with Juanita W. Braddock, the two schools' principal. At the same time, McKenzie's top three associate superintendents were swapping places with the principals of three other schools.

It was all part of what McKenzie called a "soul-searching" and "team-building" effort aimed at identifying school shortcomings and developing rapport between administrators and teachers who, she said, have a "severe morale problem" due largely to the system's recent reductions in force.

During the visit, McKenzie encountered both the best and the worst of what the city public schools have to offer. There were foreign students enthusiastically learning their numbers in English, well-behaved native students, and teachers who got to work an hour early.

There also were problems common to many schools, such as a lack of supplies and office help, safety problems on the playground, and teachers who feel their work goes unappreciated.

After hearing several teachers at Ross complain about the problems of having to "share" a principal with Stevens as a cost-saving measure, a visibly disheartened McKenzie remarked, "You know, this job requires so much giving, I wonder how long I'll be able to keep up with it. It requires me to give so much positive reinforcement to people. I wonder how long it will be before my 'trickle down' theory comes about and people give this kind of reinforcement to each other."

Since September, McKenzie has maintained a hectic schedule of meetings with teachers, principals and parents in which she has acted as a kind of cheerleader for the public schools, spreading a spirit and enthusiasm that she says must start in the superintendent's office and then "trickle down" to the teachers and students in the schools.

McKenzie attends two to three Parent-Association meetings a week and has started a system-wide employe newsletter in order to build morale, according to her spokesman, Janis Cromer. On Tuesday, the superintendent held the first of what she says will be a series of gripe sessions for teachers.

McKenzie arrived at Stevens, located at 21st and K streets NW, about 7:45 a.m. and was surprised to find that some teachers and students already were there, even though school does not start until 9. Those students have parents who drop them off early, then go to work in the office buildings nearby.

Ross, at l7th and R streets NW, and Stevens have a combined enrollment of about 360 students. They were picked for yesterday's program by lottery.

Ross has a high percentage of Spanish-speaking newly arrived Latin American students who live in the Adams Morgan area and along l7th Street near Dupont Circle. Stevens, the school once attended by Amy Carter, also has a large number of foreign students whose parents are diplomats here.

What kind of principal was McKenzie? "She was really nice, but it's kind of hard to tell," said Stevens sixth grader Robert Williams. "She was just here for today."