When Prairieville Middle School students came back from the Mardi Gras holiday Wednesday, they found themselves attending classes in a new two-story building.

With a multiyear, $15 million project drawing to a close, construction workers have been a common sight on the campus since 2012 when work began in the first phase of the project, which included a new cafeteria and kitchen that opened in 2013.

The students watched workers build their new school while they attended classes in a 50-year-old building. The school had enough property to construct the new classroom building on the campus while students attended classes in the old building.

“We flipped this campus from an old campus to a new campus,” said Chad Lynch, director of planning and construction for the Ascension Parish School District.

The second phase of construction now completed includes a 66,000-square-foot building with 34 classrooms, a computer lab, the school library and new administrative offices, all of which effectively created a new school on the original campus on La. 930, north of Airline Highway.

About 80 percent of the 892 students at the school will attend classes in the new building.

The other students will continue to go to class in two of the classroom buildings constructed during the last decade that are remaining on campus. Several other, older classroom buildings will be torn down, along with the old administrative offices.

Temporary buildings will be removed or torn down, making way for new green space on campus.

The construction at Prairieville Middle was the second-largest project funded by a 2009 bond passed by voters. The largest project was the construction of the new G.W. Carver primary school, which cost $16 million and opened in October.

The transformation of Prairieville Middle addressed drainage, parking and transportation at the school that opened in 1959, Lynch said.

A new underground drainage system put in as part of the work at the school has already solved some of the problems for the school, which was built too low 56 years ago, Lynch said.

Whenever there was a good rain, students had to walk through inches of rainwater as they went around campus, often carrying their shoes in hand, Lynch said.

There’s also a new parking lot at the school with two separate points for buses and cars.

“They were starved for parking,” said Melissa DeFee, school district construction manager for the Prairieville Middle project.

The district had hoped the new classroom building would be completed by the start of the school year, but weather and contractor and subcontractor delays pushed the opening back.

In addition to two classroom buildings already on campus, also remaining are the school’s band room, built in 2003, and the gym, which is older than that but has been “reskinned” with new metal.

Prairieville Middle is one of the school district’s A schools under the state’s grading system and had the highest score in the district for the 2013-14 school year.

“Now the facility matches the high quality of education going on,” Principal Dina Davis said.