Science Leadership Academy, the innovative Philadelphia magnet school, will relocate inside Ben Franklin High School, officials confirmed Thursday night.

The Philadelphia School District will spend $20 million to upgrade the facility on North Broad Street. Ben Franklin, a neighborhood high school, will continue to exist as a separate school; SLA will leave its current facility, a leased space at 22nd and Arch.

The co-location will happen in time for the 2019-20 school year. On Thursday, the School Reform Commission approved a $1.5 million contract for architectural and engineering services to begin the work.

Up to $12 million was already budgeted to spruce up Ben Franklin — a new roof, windows, and elevators. An additional $6 million to $8 million, including the contract awarded Thursday night, will be spent on the design and construction work.

Students, parents, teachers, and administrators from both schools will form a design committee to help shape the building, at  550 N. Broad St., and to plan for how to bring the schools together.

The upgrades will reimagine the space to suit both schools' needs. Ben Franklin has a new Career and Technical Education center focused on equipping students for advanced manufacturing jobs; SLA has won national acclaim for its project-based, inquiry-driven work, and has quickly become one of the city's most in-demand schools. For the 2015-16 school year, it received 2,234 applications for just 125 seats.

With a surplus of space and a financial crisis looming, the School District has been pushing to get out of costly leases. SLA families and students have, in the past, asked the SRC to keep the school at its current location, close to the Franklin Institute, its partner organization. Ben Franklin is just over a mile from the museum.

Chris Lehmann, SLA chief executive officer and co-principal, said the relocation is the next step in the school's evolution.

"This process will allow students, staff, and parents to create two new and modern school environments built on the notion that inquiry is the very first step in the process of learning," Lehmann said in a statement. "And all of the faculty and staff of SLA are ready to lead and work together to create greater learning opportunities for more Philadelphia students for years to come."

Christine Borelli, Ben Franklin's new principal, said the project was "exciting."

"This gives our students and school community the unique opportunity to positively shape the future of Ben Franklin," Borelli said.

Once complete, the building will house nearly 1,000 students. The six-floor school was built in 1958.