America’s best and most humble 17-year-old high school volleyball player, 6-foot-7 Sean Kelly of Loyola High, is sitting on a bleacher in the campus gym trying to explain why he doesn’t go around with his chest sticking out telling everyone he’s the best.

“I know there’s room to get better,” he says. “You should never say you’re too good unless you’re literally the best.”

Kelly certainly earned bragging rights last summer when he helped the U19 national team win the gold medal at the Pan-American Cup in Colorado Springs and was named tournament MVP and First Best Spiker.

“It feels nice to be gifted with height, but there’s always room to work on,” the Team USA captain said.

With a grade-point average above 4.0, and the size and leaping ability to sky high above any net, Kelly is set to be a player to watch in his junior season for the Cubs.

Sean Kelly of Loyola goes up for a kill.

(Brody Hannon)

“He’s wired differently,” coach Michael Boehle said. “He’s got a high IQ for games. He’s always trying to make his teammates better.”

Boehle cites a match against Newport Harbor last season as an example of Kelly’s skills.

“He hit .850, which is incredible,” Boehle said. “He had 19 kills on zero errors.”

Kelly is a perfectionist but volleyball serves as his outlet to have fun with friends. At 12 and living in Manhattan Beach, he decided to make the five-minute walk from his home to the beach so he could start to learn the sport. The rest is history. He has three sisters who played the sport. They encouraged him but it was his choice to drop basketball and baseball for volleyball.

“I saw my older sisters succeeding and I really liked playing with friends,” he said.

Dillon Klein, now at USC, was a mentor at Loyola for Kelly during the last two seasons, training him on how to lead.

“Dillon definitely inspired me,” Kelly said. “I’m trying to implement some of the things he taught me freshman and sophomore years.”

UCLA, Princeton and Stanford are among the colleges starting to gain his attention.

Among the schools to watch this season, Newport Harbor is the defending Southern Section Division 1 champion and returns UCLA commit Luca Curci. Corona del Mar, Santa Ana Mater Dei, Irvine Beckman and Manhattan Beach Mira Costa also should be in the running for a Division 1 title with Loyola.

In the City Section, defending champion Palisades and runner-up Chatsworth will again be the teams to beat.

A big match is the annual Loyola vs. Mira Costa battle March 31 at Loyola Marymount. Many of the players know each other from club volleyball and some are neighbors in Manhattan Beach. One of Kelly’s best friends “lives down the street and to the right,’’ he said.

“Playing Mira Costa is always super fun because some are my best friends off the court,” he said. “That’s the most fun week.”

One of Mira Costa’s best players is 6-8 setter Tread Rosenthal, who is also on the U19 national team.

Players from both teams who live in Manhattan Beach usually get together the next morning to exercise bragging rights.

Kelly intends to embrace expectations as one of volleyball’s most promising young prospects.

“I’ll try to do my best,” he said.