Philadelphia public-school students have made modest but steady progress since fall 2002 in math, reading and language arts on a national standardized exam, the school district reported yesterday.

The Terra Nova exam - given annually to Philadelphia students in first through 10th grades - indicated that all grades showed growth in all three subjects.

In math, 26.6 percent of students scored at or above the national average in 2002, but that rose to 40 percent in 2006.

In reading, 32.8 percent scored at or above the national average in 2002. Last year, 39.3 percent reached that mark.

In language arts, 28.3 percent of students scored at or above the national average in 2002, and 39.5 percent did so in 2006.

Despite the progress, the results also mean that in each subject, more than 50 percent of the district's students scored below the national average. That is similar to the latest results from the state's exam, the Pennsylvania System of School Assessment, given each spring. The PSSA is used by the state to determine which schools and school districts are in compliance with the federal No Child Left Behind law.

"I'm happy with the progress we've seen in the last five years," schools chief Paul Vallas said at yesterday's School Reform Commission meeting. "I'm disappointed in the fact that we are still far from where we should be. We haven't lost ground since 2002, but we have a long way to go."

To improve test scores, he said, teacher development will be revamped, instruction will be intensified across the district rather than scaled back during the last eight weeks of the school year, and a pilot summer-school program will be added at about 12 chronically low-performing schools - thus extending the school year to 10 1/2 months.

In another development, district officials and the testing company CTB McGraw-Hill are trying to determine why test results from fall 2005 were unusually high.

After three years of giving the Terra Nova in the spring, it was moved to fall 2005 to spare students from having to take that test and the PSSA within a month's time.

About half of the Terra Nova questions were the same on both the spring 2005 and fall 2005 tests, which may have created what is called a "practice effect" and which is why fall scores were higher than usual, district and CTB McGraw-Hill officials said.

"The fall '05 scores are higher than the historical trend in the district suggest that they should be," said Gary M. Schaeffer, senior director of research for CTB McGraw-Hill.

"We're going to do our [best] to try to get a rational explanation.," said Schaeffer, who came from the company's Monterey, Calif., offices for the SRC meeting.

The district has also hired two national experts who "are turning over every single rock, too, because it's to our benefit to determine what happened," said LaVonne Sheffield, the district's chief accountability officer. *