The rugby team from Our Lady and St Patrick's College, Knock, has broken new sporting ground.
They are thought to be the first team from a Catholic grammar to play in rugby's Ulster Schools' Cup.
On Wednesday, they lost a tight game in the competition to local rivals, Wellington College, by 12 points to 7.
The Schools' Cup is Ulster's oldest and most prestigious schools rugby tournament.
The final is held at Ulster Rugby's Kingspan Stadium in Belfast on St Patrick's Day each year.
The current holders are Methodist College Belfast, who also have the record number of wins in the tournament.
A new group structure for the 2019/20 competition opened the door for Our Lady and St Patrick's College to enter.
Other Catholic schools play rugby and compete in Ulster schools' competitions, but the east Belfast school are thought to be the first to take part in the elite event.
The head of PE at Our Lady and St Patrick's College, Frank Wilson, said it was the climax of many years of hard work and coaching.
"Some of the boys expressed an interest in rugby," he said.
"We worked with Ulster Branch who came in with these boys in year 8 and year 9.
"There were also parents from different clubs, like Cooke and Instonians and Malone, and they helped us out.
"This is the fruition here now where we've got to the Schools' Cup.
"This is a local derby, Belfast schools going head to head."
The players train on the school's GAA pitch and a number also play Gaelic Games to a high standard.
Team captain Oran O'Neill said that playing Gaelic football had helped his rugby skills, and vice-versa.
"The handling skills are really essential in both games," he said.
"I've also found that from a young age I was able to get experience under a high ball in Gaelic and then I would use that in rugby."
When the game kicked off, Wellington College took an early lead through a fine try by their left wing.
But Our Lady and St Patrick's hit back with a converted try midway through the first half to lead 7-5 at the break.
However, their opponents scored a decisive try in the second half to earn a hard-fought 12-7 victory.
As is customary, both teams clapped each other off at the end.
And Frank Wilson told his team he was proud of the fight they had put up.
"I'm so proud to go nip and tuck, toe to toe, with a side like Wellington College," he said.
The new structure for this year's Schools' Cup means, though, that all is not yet over for Our Lady and St Patrick's College.
They still have a chance of silverware in the Schools' Bowl which will run alongside the later rounds of the main tournament.