A new performing arts charter high school says it has sealed a deal to open in the fall at GlaxoSmithKline's former North American headquarters at 16th and Vine Streets.

Under terms that will be announced Thursday, a nonprofit associated with the Philadelphia Performing Arts Charter School has agreed to buy the curving, eight-story building for $29 million for the String Theory High School for the Arts and Sciences. It will be the first charter high school in the city focused on the performing arts.

The nonprofit, DeMedici Corporation II, expects to finance the property with tax-exempt bonds from the Philadelphia Authority for Industrial Development (PAID), according to Mary D'Anella, spokeswoman for String Theory Schools, which manages the charter.

"It's the most exciting high school this city has opened in a generation," said Angela Corosanite, chief executive officer of the nonprofit String Theory, and founder of it and the Philadelphia Performing Arts Charter School.

The charter high school will open in the fall with 350 ninth graders and add a grade each year until 1,400 ninth through 12th graders are enrolled in 2016-17.

The building, at Three Franklin Plaza, is owned and operated by Liberty Property Trust. Officials from the real estate development trust in Malvern late Wednesday were trying to confirm that a sales agreement had been reached with DeMedici II.

Records from the Pennsylvania Department of State show DeMedici II was incorporated as a nonprofit in 2011 solely to support the performing arts charter.

William P. Hankowsky, chairman, president, and CEO of Liberty, is a managing director of Interstate General Media, publisher of The Inquirer.

John Grady, president of Philadelphia Industrial Development Corp., which administers PAID's tax-exempt bond program, could not be reached for comment.

String Theory High will not only focus on the arts but also on science and technology.

D'Anella said plans call for making upgrades of between $10 million and $12 million to the 225,000-square-foot building to create a theater, performing arts studios, science labs, TV and motion-capture studios, and an automotive engineering lab.

Students will have opportunities to choose from seven areas of study: vocal music; instrumental music; ballet; theater, television, and broadcast arts; foreign languages; digital design and communication arts; and innovations in science and technology.

Glaxo has moved its headquarters from the Franklin Plaza site to a new building in the Navy Yard.

Last summer, the School Reform Commission gave Philadelphia Performing Arts Charter permission to expand to add a high school. The charter, which opened in 2000, has 1,075 K-8 students in two buildings on South Broad Street.

D'Anella said the 72 eighth graders at that elementary charter had been encouraged to apply to the charter high school and many had. She said students from across the city can apply for ninth-grade spots. The application deadline is April 30. The charter will hold a lottery to select students May 1.

She said charter officials believe the high school's Center City location will make it accessible to students from across the district.

The curriculum of the elementary charter school blends academic subjects with vocal, instrumental, and ballet lessons.

Another nonprofit - the DeMedici Corp. - owns and leases the facilities for the K-8 charter.

As a result of the elementary charter's strong academics, the SRC last year chose String Theory to convert the former Edmunds School in Frankford into a Renaissance charter school.

Under String Theory's management, the Frankford school is known as the Philadelphia Charter School for the Arts and Sciences at H.R. Edmunds. It has 1,000 K-8 students.

The application for String Theory High can be found online at www.stringtheoryschools.com.