He is an educator, fisherman, shellfisherman, sports fan, son, husband and father. The trappings of John Custer’s third-floor office in the Tisbury School, where he has been principal for four years, say as much. A Ray Ellis print of the Edgartown Lighthouse on one wall, a clock with a fish painted on it on another. A large framed collage of tickets from Boston College games and Red Sox games. Family photos and a quahaug shell filled with paper clips on his desk. A painting by a Tisbury School kindergartner featuring Mr. Custer as a stick figure with green hair and a tie.

Mr. Custer, 44, does not, in fact, have green hair (it is gray), but he does wear ties. On Wednesday this week, it was a red one with a repeating pattern of blue fish. It’s derby season, after all, and Mr. Custer is in his second stint, and eighth year, as chairman of the Martha’s Vineyard Striped Bass and Bluefish Derby. September, when the start of school and the derby overlap, is a busy time of year.

Beneath John Custer's tie beats the heart of a fisherman. — Ivy Ashe

It’s challenging to balance coordinating a tournament that last year had more than 3,000 registrants with working through the daily demands of a 330-student school, but Mr. Custer is well versed at both jobs. He credits the strong support of all his teams — the school staff, the parents, the derby committee and the derby volunteers.

If you have good people, he said, it’s easy.

Born and raised on the Vineyard, Mr. Custer started fishing before he was in first grade, but he didn’t fish the derby until 1995. That was the same year he moved back to the Island for “one last summer,” after living in Boston following graduation from Boston College. He had been working for an insurance company, which he enjoyed, but had decided he wanted to change fields and become a teacher.

“I was going to go back to school, get my teaching certification, and go find a job somewhere,” Mr. Custer said. Which is kind of what happened, he continued, except the “somewhere” turned out to be the Vineyard. He started at the West Tisbury School as a middle school social science and language arts teacher in 1997. It was his first job in education, and he loved it.

“It shouldn’t shock me — or anyone, I guess, for that matter — that I ended up in education, but it was never anything that was on my radar,” he said. Still, his father Herbert Custer directed the high school vocational program and was superintendent for four years, which likely played an indirect role.

“I’m sure I saw that he had a very fulfilling, rewarding career; I witnessed that growing up,” Mr. Custer said. “So I’m sure there was an influence, even if it wasn’t a spoken influence.” A definite spark for the career change came from running into his former teachers on his ferry trips to and from the Vineyard, and hearing them talk about the satisfaction they had from working with kids on the Island.

And when one of his former teachers retired in 2004, Mr. Custer truly came home — to the Tisbury School, which he first attended as a kindergartner (he recently found a school photo of his first class; he’s the sandy-haired kid standing in the back row). Teaching in his hometown of Tisbury “felt right,” he said. He taught fifth and sixth grade social studies.

John Custer--principal of Tisbury School, chairman of Striped Bass Derby. — Ivy Ashe

“Now that I’ve been doing it for a number of years, I can’t imagine doing anything else,” Mr. Custer said.

Education also led him to the derby, in a roundabout way. Mr. Custer’s father was friends with longtime derby committee member Sancy Pachico, also a longtime educator, and Mr. Custer remembered that the reason Mr. Pachico got involved was because he wanted to help students.

“The most important thing the derby does is the scholarships for high school graduates,” Mr. Custer said. When he was asked by Ed Jerome to join the committee, he didn’t hesitate. He became chairman for the first time in 2003.

“I’d only been on the derby committee for a short time,” Mr. Custer said. “I got through it with a lot of help and support from the whole committee. Steve Morris in particular was huge — still is. He’s my go-to guy.” The number of people it takes to manage the derby is extraordinary, he said.

“I enjoy being chairman because you kind of get to see how the whole derby operates . . . it’s huge,” Mr. Custer said. “We couldn’t do it without the staffers,” he continued, citing the work of weigh station coordinator Amy Coffey.

The first and second years as chairman flowed into a third, and a fourth and fifth. But in the sixth year, Mr. Custer was working toward his school administration certification, on his way to becoming assistant principal of the Tisbury School. He remained on the committee, but did not return as chairman so he could focus on learning the administration ropes.

The switch from teacher to administrator was eased by working with then-principal Richie Smith, who is now principal at the Oak Bluffs School.

“He was just terrific in mentoring me, daily,” Mr. Custer said. “The culture here that he helped create and strengthen was one of shared leadership.” It was more difficult to move from assistant principal to principal simply because he didn’t get to interact with the students as much. So he moved his office to the third floor, more “in the fray.” His favorite part of the school day is supervising lunch, because he gets to see all of the Tisbury School kids.

Walking the walk, icing the ice, Principal Custer dives into ice bucket challenge with his school. — Ivy Ashe

Mr. Custer’s daughters Isabelle, 13, and Alison, 10, are both students at the school.

“I think they probably like me being here — I haven’t heard otherwise — but I also think that during the day they don’t want Dad interfering with them,” he said. Another favorite part of the day is the drive to school, when he does get to be Dad instead of Mr. Custer.

“It’s a nice time for me,” he said.

The Custers occasionally participate in the Kids Derby (which Mr. Custer fished as a youngster, too), but ironically there’s little fishing that goes on during this time of year. There just isn’t time. Mr. Custer fishes in the summer, when it’s not as busy.

“I love to eat fish, and my family does,” he said. “There’s something really, I think, just cool for lack of a better term, about eating what you catch.” He likes to prepare striped bass and black sea bass, both family favorites, but lately his wife Amy has also been testing fluke recipes.

Next month, there will be scallops and oysters, when recreational shellfishing season opens.

“As much as I love fishing, I’ve come to realize that shellfishing is a lot better for your ego, because you always come home with something,” Mr. Custer said. “If your time is limited, you want to make it count.”

But if your time is unlimited, he said, just the beauty of being out on the water is enough.