Parents of some Pittsburgh elementary school students will find an unwelcome surprise -- unusually low marks in reading -- when their children bring home report cards Nov. 17.

Because the Pittsburgh Public Schools this fall introduced a standardized grading system and what it described as a more rigorous reading program, some students have seen their performance slip on classroom tests.

That will translate into lower grades on report cards than parents are accustomed to seeing, said Susan Sauer, curriculum supervisor for elementary reading, and Barbara Rudiak, executive director for 18 district elementary schools. Some parents already have noticed a drop in their children's test scores.

"This has created a certain amount of controversy with principals, parents and teachers," said Dr. Rudiak, who is project manager for the "Treasures" reading program, purchased from Macmillan/McGraw-Hill for about 13,250 students in kindergarten through grade five. The program is also used in elementary classrooms at the district's K-8 schools and accelerated learning academies.

Aligned to state learning standards and the federal No Child Left Behind Act, the program should boost student performance on the Pennsylvania System of School Assessment, said Richard Sternberg, principal of Grandview Elementary in Allentown and president of the Pittsburgh Administrators Association.

Ms. Sauer and Dr. Rudiak said changes in elementary reading complement the district's "Excellence for All" plan, which includes a 2009 deadline for academic improvement.

Before this school year, each teacher decided what constituted an "A" or other grade in elementary reading. Some teachers gave more weight to take-home work than colleagues did, and some teachers designed their own tests because they didn't like those provided with the previous program, Harcourt "Collections," Ms. Sauer and Dr. Rudiak said.

Such discretion has been eliminated as the district standardizes instruction within a school and among schools to promote equal treatment of students, they said. All teachers now use tests provided with the "Treasures" program.

Initially, the district decided that the weekly tests would make up 40 percent of a student's grade; unit tests, given about every five weeks, 50 percent; and assignments, 10 percent.

But that formula quickly yielded so precipitous and widespread a drop in grades that officials revised the system. In hindsight, Dr. Rudiak said, the initial formula gave too much weight to tests -- and did so when the format was brand new to students and teachers.

Pittsburgh Federation of Teachers President John Tarka said his members advocated for a change in the grading system to keep students from being unfairly penalized. While cautioning that "we have more work to do," he said the revised formula is better for students and restores some of the flexibility teachers need to be effective.

"There's a fine line between there not being guidance and something being too rigid. Neither one is good," Mr. Tarka said.

Assignments now make up 30 percent of the grade, while unit tests and weekly tests each account for 35 percent. Ms. Sauer and Dr. Rudiak said they still expect some students to have lower-than-typical report card grades, in part because of the rigorous "Treasures" program.

While the Harcourt program tested students on passages they had read before, "Treasures" requires students to apply comprehension and other skills to unfamiliar texts. It includes more nonfiction passages than the old program.

Some parents learned about the program changes through progress reports and teacher conferences, but principals have been asked to send home a letter in the next day or so to further explain the situation.

"Treasures" was introduced this year and, besides Pittsburgh, it's used in Chicago; Boise, Idaho; and Wichita, Kan., among other districts. Pilot studies have shown improved student achievement, Macmillan-McGraw Hill spokesman Tom Stanton said.

Ms. Sauer and Dr. Rudiak said additional adjustments to the grading system may occur in the future. Mr. Sternberg said students are catching on.

"As a matter of fact, they're starting to do better now," he said.