The school is more than 75 years old and the New Brunswick government intends to replace it with a new facility on the outskirts of the city.
Anne-Marie Picone Ford, a parent and organizer of the protest, said passing cars honked in support as some 200 protesters rallied around the school Monday evening.
She said most were clad in purple — one of the school's official colours.
"It was really, really wonderful," she said in an interview after the protest.
"People actually were going right up to the building and hugging it. It was great."
The Department of Education committed to building a new school after Moncton High School was closed in 2010 over health and safety concerns. The inner-city school reopened to students in the fall.
Some parents have protested the planned move, saying the school needs to remain downtown rather than the Royal Oaks site about eight kilometres from the city's centre.
Picone Ford said moving the school will be a hardship for many teenagers.
She said that students in the city have been able to walk to their part-time jobs and extracurricular activities, but the new school will be too far outside of the city for that to continue.
Then there are the memories.
"I've never seen or heard of a school with as much pride as this school has," said Picone Ford, a mother of seven, including five Moncton High graduates.
"There's so much that's going to be lost, the culture of this school is so important ... It would never be the same out there."