HARRISBURG -- In the mid-1990s, the Coatesville Area School District traded in its traditional high-school schedule for a new format with fewer classes, but longer class periods, hoping that more in-depth classroom study would produce higher test scores.

Now, with the nation's public schools facing intense pressure to improve math and reading test scores under the federal No Child Left Behind Act, administrators in the district near Philadelphia have concluded that providing four nearly 90-minute periods of "block scheduling" hasn't helped.

In February, the school board approved a return to a schedule of seven periods of approximately 40 minutes. The change will take effect in September.

"In our circumstance, it was an educational decision on how kids best learn," said James T. Scarnati, the district's superintendent for the past three years. "We changed in order to help us become better and more proficient at what's being measured by No Child Left Behind."

Block scheduling was among a variety of alternative schedules endorsed by the National Education Commission on Time and Learning in 1994. The commission urged schools to rethink traditional schedules so students could spend more time on core subjects such as English, math, science and history.

It is unclear how many schools nationwide adopted block scheduling -- the number in the state also is unknown, according to the Pennsylvania School Board Association -- and statistics on those that have tried and abandoned it are even harder to come by.

Additionally, no broad national studies have been conducted to determine whether block scheduling improves standardized test scores, said Carol Freeman, a research associate with the Center for Applied Research and Educational Improvement at the University of Minnesota.

Block-scheduling research compiled by the center has generally focused on either one school district or one state, with varying results. For example, while a 2003 study of Connecticut high schools found that performance on state tests "may even improve" under block scheduling, a 2002 comparison of two South Carolina high schools -- one with block scheduling and one with traditional scheduling -- found no significant difference in reading or math scores.

"Block scheduling ... makes it easier for teachers to do the kinds of activities that can research an objective. If they want to stand and deliver a lecture, then you might as well have a shorter class," Freeman said. "A schedule can't push learning."

At Coatesville, math scores are a concern, Scarnati said. Coatesville's average score on the state's 11th-grade math test has fluctuated between 1250 and 1280 over the past several years, according to state Education Department records. The minimum score that students must attain to demonstrate they can perform at their grade level is 1310.

Scarnati said the timing of the test may create difficulties for students. Coatesville's block scheduling enables students to take a year's worth of classes in one semester, and the test is given in the spring.

"The gap occurs by children taking a year's math course in the first semester, then they probably more than likely don't take another course until the next year. There's no chance to remediate [any problems]," he said.

Coatesville physics teacher Dave Fenimore believes the longer periods work for English, social studies, and "special subjects" like art and music, but not for math and science.

Although it is supposed to enable teachers to offer a wider range of classroom activities in one period, Fenimore said he primarily stuck to lecturing because he believes students should learn how to listen and take notes.

"It has caused problems for me, because in a field like physics, you introduce a topic, and you need time to absorb that concept," said Fenimore, a 17-year veteran. "I ended up introducing multiple concepts in class. I've been arguing that it's akin to dumping five gallons of water on a drowning man."

James Buck, a 16-year-old junior, said block scheduling was "a relief" when he entered high school, because the pace felt less hectic.

He expects he will adjust to more classes in shorter periods next year, but said many students are anxious about the change.

"My personal opinion is that they're moving too quickly," Buck said. "If they told us this year that they would start implementing it for the class of 2006, I wouldn't mind."