BALTIMORE -- For 150 students who return to a Baltimore high school today, there will be no 50-minute class periods, no grades and no paper and pencil examinations.

Instead, the Walbrook High School students will be required to demonstrate what they have learned in exhibitions, make their own discoveries and spend longer days in school as part of an experiment aimed at revamping American education.

Walbrook is among 46 schools across the country that are trying to put into practice the educational theories of Brown University's Theodore Sizer, whose Coalition of Essential Schools program emphasizes personalizing education and "students as workers."

"We're not preparing them for special occupations but to think through situations," said Principal Samuel Billups, a supporter of the program that started last year.

The first and second level (ninth and 10th grade) students involved in the program either volunteered or were chosen randomly from the 2,000 pupils at the predominantly black urban school.

Students advance to the next level after they have shown mastery of the skills through projects designed to demonstrate their understanding. Grades are replaced with frequent written evaluations and progress reports from teachers.

"The program may take a little longer at first," Billups said. "But the long-range costs level out with greater retention and greater achievement."

Walbrook students in the program take biology, English, urban growth and math in the first year and chemistry, U.S. history, French, geometry, English and health education in the second. The program is expected to be extended to the last two years of high school.

Students can also take electives and attend early morning tutoring classes, but that often means going to school at 8 a.m., earlier than most Walbrook students, and not leaving until 4:30 p.m., 90 minutes later than their counterparts.

"In traditional classrooms, the teacher is the giver of information," said Marian Finney, the program's coordinator. "{Here}, the students have more responsibility. They are taught concepts and they demonstrate them. The teacher acts as the coach and reinforces" what they have learned.

For many students, it is the first time they must be responsible for learning, she added.

Sophomores Monica Harrid, 17, and Patricia Westbrook, 15, say the program was hard the first year, but they have come to appreciate the individual attention and progress they are making.

"Sometimes friends tease me about coming in early, but I feel I'm learning more," said Westbrook, who credits the tutoring and smaller class size.

Westbrook said she enjoys writing and reading last year's assignment, Shakespeare's "Julius Ceasar." She said she is looking forward to geometry, French and chemistry this year.

"But it's more work," admitted Westbrook, who also joined the track team and junior Navy ROTC program.

Harrid said the program tries to get students to be responsible and has made her a better thinker.

"The buck stops here. If you want to learn, you learn," said Harrid, who also is in the junior Navy ROTC program. "What we do now will really help us in college."

The two students say the program has meant more involvement for parents as well.

Patricia Westbrook, Nicole's mother, said there is more one-on-one contact with teachers and more learning opportunities.

"Nicole has been able to do so much that I never even dreamed about," Patricia Westbrook said. "I'm proud of her and grateful" to the school.

Billups dismisses critics of Sizer who say the program does not produce measurable results and costs more than traditional programs.

"As for measurable results, if you take a hard look at urban schools, the only direction to go is up," he said. "This is an excellent opportunity that will show improvement."

Last year, the program was funded through a $50,000 foundation grant and $15,000 in state money. The program will run on a $50,000 grant this year.

"The additional cost of the program evens out when {you} consider the dropout rates, if we can keep 100 students in school who might become dropouts," Billups said.