Parents at Silver Spring International Middle School worry the school's plans to cut its eighth period will worsen the school's achievement gap.

The school plans to go from eight periods -- a block schedule with four classes a day -- to seven periods beginning in fall 2014. School leaders will spend the next year deciding how those seven periods will be arranged -- whether in a single, seven-period day or in blocks -- and which class will be cut, said Principal John Haas.

This year, all students take math, English, social studies, science, physical education and health. For the remaining three classes, students can choose art or music electives, a foreign language, or a second math or reading class if they need extra help in one or both of those areas. There are roughly 150 students in each of the math- and reading-intervention options, Haas said.

Teachers recently voted to reduce the number of classes that students take each semester to seven, and a committee of officials from Montgomery County Public Schools and its unions approved the decision.

Teachers were concerned that students are not spending enough time in core classes, said Montgomery County Education Association President Doug Prouty, who also has a daughter attending the school in the fall.

The school also lacks enough teachers to make the eight-period schedule work, officials said.

Teachers' contracts require them to teach no more than

five periods a day, or over two days for a block schedule, Prouty said. For the last several years, some teachers have voluntarily taught a sixth class, but "over time, [they] have decided that it was reducing their ability to be able to address the needs of all students."

To continue the eight-period day with teachers teaching five periods and keeping class sizes the same, the school would need to hire roughly 0.7 additional full-time teachers for every 100 students, which isn't in the budget, said MCPS spokesman Dana Tofig.

Worried that the change will hurt minority and low-income students, who tend to struggle more than other groups with math and English, a group of parents has filed a complaint challenging the school system's decision.

Of the school's 916 students, 44 percent receive free and reduced price meals, and 62 percent are black or Hispanic, according to MCPS data. The data show that the portions of these populations finishing algebra with at least a C by eighth grade are much smaller than those of their white, Asian and higher-income classmates.

"After the eighth period was implemented six years ago, [the school] went from a failing school to a very successful one," said Margy O'Herron, who has a daughter in seventh grade at the school and a son entering sixth grade next year. "MCPS [is] saying repeatedly that it is looking for ways to close the achievement gap, but at the same time discontinuing the very structure that made our school successful."

But Haas emphasized that the school has not decided which class might be cut. The extra help in math and reading could remain while an elective goes.