School days for Baltimore County high school students will be significantly different next year when Superintendent Dallas Dance imposes a uniform, eight-class schedule throughout the district.

The move allows students to squeeze in more lessons. That could help transfer students who had to drop classes when they moved to schools with shorter schedules or failing students who are falling behind in the credits they need for graduation, proponents say.

School officials said the shift also makes better use of the teaching staff.

"Our focus is to give our students as much access and opportunity as we can," said Maria Lowry, assistant superintendent in charge of high schools.

But critics say the change will burden teachers with more work — and could lead to position cutbacks. Some high school teachers will be required to teach six classes per semester, instead of five, and one consultant found that 100 fewer teachers would be needed under the new schedule.

The change comes on top of several other initiatives, including a new curriculum and new teacher evaluation system that requires teachers to document student achievement.

"Right now, we have so many new initiatives. It is one new thing after another after another," said Abby Beytin, the president of the Baltimore County teachers union. "Where does the workload end?"

Schools will be able to choose between scheduling eight 40-minute periods in one day or four 90-minute periods with different classes on alternating days, called a block schedule.

Many schools are expected to opt for the block schedule, which gives students more time to delve into a subject. With such a schedule, students would have four classes on Monday and four different classes on Tuesday. The schedules would then continue to alternate.

Each schedule would allow students to take eight subjects a semester.

About 11 of the county's 25 high schools — and half its high school population — are on a traditional schedule of seven periods plus lunch. Some of the school system's highest-performing schools, including Towson, Eastern Tech, Dulaney and Franklin, are on the seven-period schedule.

Also next year, middle school students will be required to take seven classes a semester; most already do.

Before making the changes, Dance hired a consultant, Scholastic Scheduling Solutions, or S3, for $285,000 to survey schools and study different options for the school system.

In the analysis, S3 found that the school system would need about 2,720 high school teachers if it required that students take eight classes and teachers handle six. That's about 100 fewer than if the system imposed a uniform, seven-period day, according to the analysis.

S3 also found that the eight-class schedule gives students significantly less class time each year for any given subject.

Lowry said the decision to go to an eight-class schedule wasn't made to reduce staff or cut costs. She said the number of teachers needed would also depend on what electives students sign up for.

Beytin, the union president, warned that any reduction in the teaching staff would be hard on schools, particularly the highest-performing schools, which have had the most severe cutbacks and now have larger class sizes.

Parents and teachers have complained that many classes have more than 30 students.

"The high schools are still reeling from the number taken out of their ranks in the past two years," Beytin said.

But Billie Burke, an assistant superintendent in charge of professional development, said the change to next year's schedules actually could mean smaller class sizes in some schools.