A permit has been approved for a private school in Marietta, Ga., that wants to lease some acreage on the property of a future $300 million mixed-use development. Site preparation for that development is already underway. The school hopes to be operational by August. The 82-acre project will include retail and office space, town homes, apartments, single-family homes and condos. The project's phased construction could begin in 2014 and take 10 years to complete.