Pittsburgh Public Schools officials say a core curriculum for grades six through 12 has become more engaging, more rigorous and better tailored to city students since teachers were recruited for writing duties last fall.

But the curriculum -- for which New York-based Kaplan K12 Learning Services initially was to be paid $8.4 million -- remains a work in progress, with material delivered to teachers shortly before it's taught, teachers falling behind pacing schedules and benchmark test scores raising questions about the curriculum's effectiveness.

"Our work is far from finished," said Paulette Poncelet, the district's chief of research, assessment and accountability.

Benchmark tests track student progress through the year. On the most recent ones given between Oct. 22 and Jan. 25, overall scores ranged from an average of 45.1 percent correct in U.S. history to 69.6 percent in eighth-grade English.

The tests are supposed to indicate whether students are grasping course material, but the scores aren't easy to interpret. The low scores could reflect a problem putting the curriculum in place.

They could mean that higher expectations are making students struggle or that the tests aren't precisely measuring what's taught in class.

"It is possible that the new curriculum and benchmark assessments associated with the curriculum have raised the bar for students considerably, and we may see some increases in the PSSA results," Dr. Poncelet said, referring to the Pennsylvania System of Student Assessment, mandatory state tests in reading, math, writing and science in certain grade levels.

Dr. Poncelet said it's been no small feat to develop, implement and test a curriculum at once, a balancing act prompted by low PSSA scores and the district's fast-paced improvement efforts.

Kaplan's three-year contract called for it to write 27 courses in English, math, science and social studies and an algebra lab.

Teachers criticized the first nine courses and the algebra lab, all developed by Kaplan and introduced last school year, saying the material wasn't rigorous enough and had to be covered at an unacceptably rapid pace. District officials had their own complaints, including benchmark tests that they said didn't closely mimic the PSSA.

The district cut $2.4 million from Kaplan's contract last summer. It reallocated $1.4 million for technical assistance from the University of Pittsburgh's Institute for Learning. It also reallocated $1 million for teacher feedback committees and paying 51 teachers and coaches to take over much of the curriculum writing.

The district and the university provided curriculum training to the 51 employees in August, then put them to work retooling the initial courses and algebra lab and developing 12 courses for this school year.

The final six courses, to be introduced in the fall, also will be developed by teachers and coaches.

"I'm happier with things than I was a year ago," said Linda Lane, deputy superintendent for instruction, assessment and accountability, noting she's visited classrooms where instruction was insightful and interactive.

Mary VanHorn, the Pittsburgh Federation of Teachers' vice president for elementary schools, said, "Year two is much better than year one."

Philip Weinberg, Kaplan general manager, said he wasn't sure how teacher-produced courses differed from Kaplan's courses last school year. But he said the teachers' involvement is an important development.

In the new U.S. history course, a unit on the 1930s and '40s traces the effects of the Depression and World War II on African-Americans, Japanese-Americans and other groups. It uses local archives to show the period's effects on Pittsburgh, and students play a stock market game and analyze political cartoons to step into the period.

Similar approaches can be glimpsed in the other new courses.

The district's writers are infusing courses with the perspective of minority groups, hoping to make material more relevant to the city's predominantly African-American student body. To add rigor, the teams are incorporating the Institute for Learning's guidelines for high-level, interactive learning.

Kenneth Smith, a Pittsburgh Oliver High School teacher who's helping to write the U.S. history course, said students are adjusting to the shift in learning.

"It was culture shock for the students. It was culture and academic shock for some teachers," Mr. Smith said.

Kaplan still has a role in the project, writing overviews for the courses and establishing learning goals for each unit of instruction. Teachers and coaches are writing lesson plans to meet the learning goals. Kaplan and teachers collaborate on benchmark tests.

According to Kaplan's outline for U.S. history, teachers were to cover the Depression, New Deal and World War II in a five-week period. But Mr. Smith said not all teachers had completed the material in the time allotted, a sign pacing schedules need additional revisions.

Benchmark tests also are tied to the pacing schedule. Because teachers are falling behind, officials must try to adjust the tests so students aren't asked questions about unfamiliar material, Dr. Poncelet said.

Ms. VanHorn said teachers are supposed to get material three weeks before teaching it.

"Sometimes, that doesn't happen," she said.