MEXICO — As sixth, seventh and eighth grade students walked into their new school for the first time Jan. 20, they were greeted by balloons, live music and teachers clapping and cheering for them.

It was a day of celebration as classes officially began at the $92 million Mountain Valley Community School at 58 Highland Terrace.

“What makes today extra special is that no one has ever gone to school here before,” Principal Carrie Luce said at an afternoon assembly. “No one has ever sat in your classroom. No one has ever walked these hallways as a student. No one has ever learned, laughed, struggled or succeeded in this building until you. That means you are first. You get to decide what this school feels like.”

The school will house an estimated 1,000 students from Rumford, Mexico, Roxbury and Hanover in Regional School Unit 10. The school replaces Rumford Elementary School in Rumford, and Meroby Elementary and Mountain Valley Middle schools, both in Mexico.

“This is your school. Over the last year and a half, you’ve been learning in different buildings — different classrooms and different spaces,” Luce said. “You adapted and made the best of situations that weren’t always easy. And today, finally, you’re all here together, under one roof, in a school that was built just for you.”

Students entering the building for opening day were greeted by Assistant Superintendent Matt Gilbert playing live music in the lobby. The area was decorated with balloons and streamers. A welcoming committee of law enforcement and teachers in prekindergarten through eighth grade set the tone for the day.

“It’s my best opening day in my 20 years of education,” Luce said. “The other novelty is how many principals and teachers get to have a brand new school?”

“We have had so many discussions and planning sessions leading up to today that I felt pretty confident about how smoothly things would go,” Luce said.

At the assembly, Luce talked to students sitting on bleachers in the gymnasium.

“You get to help set the tone for how people treat one another here,” she said. “You get to help decide whether this is a place where students get to feel safe, respected, challenged and proud to belong. That’s a really big deal and a real big responsibility.”

The school, Luce said, is more than the building itself.

“This building is beautiful, but a school is not defined by walls, floors or lockers,” she said. “A school is defined by the people inside it. You’ve already been through a lot together. You’ve proven you can handle change, that you can keep going and that you can grow. Now you get a fresh start in a new space, and with that comes a chance to be intentional about the kind of community who want this to be.”

The prekindergarten to grade five students are scheduled to start classes Jan. 27, one day later than planned due to a major snowstorm the day before.

“Think of all the little ones who are going to be joining us next week, and they’ll be looking up to all of you,” Luce said. “You’re the role models of this school.

She issued a challenge to the students.

“Be kind, especially when it’s not easy. Be respectful, to people, to the building and to yourselves. Be responsible, knowing you are authoring the next chapter of this school,” Luce said. “Be proud of this place, because it belongs to all of us. Welcome home, middle schoolers, and welcome to the start of something really special.”

After the assembly, each grade celebrated with a cake. The cake for the eighth grade, which had temporarily been holding classes in part of the bus garage at the high school, was topped with icing that read “From the Garage to Greatness. Welcome to the Mountain Valley Community School, 8th Graders.”

RSU 10 also includes students from Buckfield, Hartford and Sumner who attend schools in Buckfield and Sumner.