For the first time in its nearly 100-year history, John Bapst High School in Bangor is planning to expand.

The plans include razing the former Jewish Community Center next to the school on Somerset Street and replacing it with a two-story, 15,000 square-foot gymnasium and fitness center that will cost $3.5 million. The school has owned the building since the 1990s and uses it primarily for storage.

But the new gym will only be used for practice, Head of School Mel MacKay said, because the tight residential area cannot accommodate more than 25 parking spaces. Basketball games will continue to be held at the Cross Insurance Center.

The current gym on the bottom floor of the six-story school, which has been virtually untouched since the original construction of the building, will be renovated and turned into a new dining hall and kitchen for $950,000. The adjacent locker rooms will be converted into a $500,000 robotics and engineering classroom.

The entire endeavor will cost $7.5 million — $1 million of which will be added to the school’s existing $1.3 million endowment, which pays for student scholarships and other operating costs. Because the school is private, it must use its own money and raise funds to pay for the project.

$3.4 million already has been raised for the campaign, mostly in the form of donations from John Bapst alumni, MacKay said.

The plans for renovation, which have been in the works since 2015, are long overdue, he said.

“We are eager to give students 21st-century facilities,” he said.

John Bapst was built in 1928 on the edge of downtown on Broadway and served for about 60 years as a co-ed Catholic parochial school. In 1980, the school re-opened as a secular, private college-prep high school. Today, John Bapst has 470 students from Maine and other countries, including China, South Korea and Vietnam.

Enrollment fluctuates year to year, MacKay said. At most, the school has had 515 students.

In 2011, the school began boarding international students and some in-staters who lived outside commuting distance. Today, the school boards about 50 of its students — 90 percent of which are from other countries — housing them in seven nearby residential buildings on Broadway and French Street that the school owns.

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