The Brooklyn Lab Charter School has leased a new location in Dumbo Heights near its other locations in Downtown Brooklyn.

The upcoming 81,648-square-foot middle and high school will have the entire second through fifth floors of 77 Sands St. along with some office space on the 12th floor and a canopied entrance.

The multibuilding, 750,000-square-foot project is being redeveloped by Kushner Cos. together with RFR and LIVWRK. The group purchased the connected campus from the Jehovah’s Witnesses in 2013 for $375 million.

Since then, the partners have poured in another $100 million in upgrades and tenant work, and to create 50,000 square feet of retail – now filled with lively coffee shops and other small retailers.

RFR later bought the residential building for $25 million; Normandy Partners purchased another for $100 million; and last year, the remaining trio bought out the Invesco Mortgage Recovery Fund for $600 million.

Scott Klau of Newmark Knight Frank represented the school which focuses on college preparation.

The Dumbo Heights ownership team was repped by another Newmark team of Whitten Morris and Joseph Sipala of its new Brooklyn office. Sources said the rent was in the mid-$50s per square foot.

The buildings are now about 95 percent leased with tenants that include WeWork, Etsy and plenty of TAMI offices.

Kushner and Newmark did not return requests for comment to the brokers.

The school expects to open in September with its sixth through 10th graders.

“We’ve been on a 3.5 year journey to identify a permanent home for our high school and looked at 17 properties carefully and after extensive negotiation landed on 77 Sands,” said Eric Tucker, the Lab’s executive director. “We really love the space because it is part of our broader campus and is a spacious and open environment.”

AKA Studio is the architect, with students and parents supplying input to the final design which is expected to include a performing arts space, a cafeteria and other multipurpose rooms.

The 12th floor will be dedicated to student conference, presentation and exhibition spaces for their advanced placement projects.

“It’s important that the students have spaces that reflect the innovation economy,” added Nick Dominguez operations manager. Since the building is filled with tech companies,” Dominguez says, “The building will provide Lab scholars with an environment they will increasingly encounter in real life.”