As Boys’ Latin’s varsity lacrosse team filed onto the school’s J. Duncan Smith turf field before practice on a sunny Thursday afternoon last week, almost every player had an interaction with Mark Warns Jr.

It stands to reason why the players would want to share a laugh or a fist-bump with the Lakers’ No. 1 fan — an official designation he garnered at a ceremony 10 years ago.

After all, Mark Jr. is a beacon of pure enthusiasm for all things BL, and is about as popular of a figure that there is on the campus that straddles both sides of Lake Avenue near the northern terminus of Roland Avenue.

“Mark is the definition of unconditional love,” said Brandon Gaines, a 1972 Boys’ Latin grad and an avid fan of the positive attitude that Mark Jr. brings to BL’s students, teachers and administrators.

Mark Jr., 37, who acts more like an enthusiastic middle-school aged student, was first affected by urea cycle deficiency disorder, a rare genetic malfunction caused by the lack of an enzyme in the urea cycle — which removes ammonia from the bloodstream — as an infant.”

He went into a coma and suffered brain damage,” said his mother, Lynne, a former Friends Middle School administrator, about Mark Jr.’s cognitive challenges.

His issues never prevented him from becoming a fixture on BL’s campus, often walking from his parents’ home in the Lake Falls neighborhood to the school.

Indeed, on Thursday, Mark Jr. became even more immersed in the school community after the Boys’ Latin Alumni Association made him an honorary member at an assembly following senior speeches.

Lifelong friend and 2013 BL alum Jake Walsh presented Mark Jr. with the official certificate, noting how “gratifying and cool it was for him to receive that official recognition while interacting with the BL family. Mark is the most caring and thoughtful person I’ve ever met.”

Mac Kennedy, BL’s director of alumni relations, told the gathering on Thursday that the honor bestowed on Mark Jr. was for “the person who loves this school more than anything else, who wears his BL gear everywhere and who has an unconditional passion for BL…the one, the only, Mark Warns.”

The reaction from the audience was swift and loud.

”The whole group of guys jumped up and went crazy,” Gaines said, “They went nuts. There’s not a person in the school who doesn’t love him. He’s like the mayor of BL.”

A more formal ceremony replicating Thursday’s event will be held in the Smith Alumni House on Saturday preceding the Lakers’ lacrosse game against Archbishop Spalding on Homecoming Day.

Mark Jr. rarely misses a home lacrosse game, and attends some away games as well, cheering on the No. 3 team in the Banner/VSN Top 15 boys’ lacrosse rankings.

”He’s always the guy here supporting us,” said Jacob Pacheco, a talented midfielder and University of Pennsylvania commit who shares captain duties with fellow seniors Kyle Foster, Jackson Walsh and Thomas Moxley. “He’s always telling us to beat (archrival) St. Paul’s. He’s as much a part of the team as any of us. When we’re walking off the field after a game, he always has a smile for us, whether we’ve had a big win or a tough loss.”

Mark Jr. was beaming when he was asked about how he felt about being a new member of the Boys’ Latin Alumni Association.

”It was awesome,” he said, noting that he was nonetheless “nervous” about being the center of attention.

There is an ironic component to Mark Jr.’s affiliation with, and devotion to, Boys’ Latin, considering that his father, Mark Sr., was a highly regarded attackman on the City team that bowed to the Lakers in the now-defunct Maryland Scholastic Association A Conference lacrosse championship game in 1966.

”Losing to Boys’ Latin broke my heart that day,” he said. “But little did I know that someday BL would save my son. He was a young man with a disability who didn’t have much of a social life, other than his family. Being a part of BL has transformed his life.”