A top Philadelphia School District magnet will expand next fall. A $147,000 grant from the Philadelphia School Partnership is helping to paying for the addition of seventh and eighth grade classes to the Carver High School for Engineering and Science in North Philadelphia.

The planning grant was announced Thursday by the nonprofit known as PSP.

The plan was hatched last year, Principal Ted Domers said, when district officials approached him about possibly growing the school to add more high school students. But Domers had another idea - what if they added grades, offering the school's program to middle school students? After working with district officials, he and others reached out to PSP to see if they might qualify for a grant.

The school will add 120 pupils beginning in September 2015. Carver's current building has room to house the extra students.

PSP's money funds this school year as a planning year, Domers said. He and a leadership team have time set aside each day to work on the school expansion, and will make visits to other successful STEM (science, technology, engineering and math) schools. Carver will also work with a few district K-8 schools to learn more about teaching middle school students.

Carver, on West Norris Street near Temple University, now serves 750 students. It has won the national Blue Ribbon of Excellence award for its academic strengths.

Domers, a former district teacher now going into his second year as Carver's principal, is beyond excited, he said.

"It's going to be amazing," he said in an interview. "The opportunity to innovate is amazing."

Some of the school's introductory classes will be tailored to seventh and eighth grade students, Domers said, allowing more possibilities for high school juniors and seniors - internships, projects, and other real-life work.

"Carver is achieving well above both city and state averages in math and reading while serving a diverse student body," Jessica Pena, director of PSP's Great City Schools Fund, said in a statement. "We see in Principal Domers a passionate leader who understands that teacher, community, parent and alumni involvement are pillars on which excellent schools are built. We are excited to support plans to give more Philadelphia students an opportunity to attend this great school."

The investment in Carver - announced along with a $246,000 grant to the Friere Charter School to help pay for a strategic growth plan and new assessment systems - means that PSP has now disributed $35.4 million to fund growth in high-performing city schools of all types.

Of that sum, $11.5 million has gone to district schools. The organization was founded with the goal of raising $100 million for good schools of all stripe. PSP aims to move 35,000 city schoolchildren from struggling schools into strong ones.

Some city education watchers are wary of PSP, believing that the organization is pro-charter and anti-teachers' union at the expense of most traditional district schools.