Many in the standing-room-only crowd of 3,500 at Liberty High School for the semifinals of the Les Schwab Invitational came to see nationally ranked Sierra Canyon of California and its star player, Bronny James.

But by the time the West Linn Lions were dribbling out the final seconds of a shockingly decisive 86-69 victory over LeBron’s son and his star-studded group of teammates, the LSI faithful in Hillsboro were on their feet for the hometown underdogs who proved they belong on a big stage.

After edging defending 6A champion Tualatin in overtime in the quarterfinals, the Lions stepped up when the competition reached another level.

West Linn (9-0) was led by the 38 points of senior Jackson Shelstad, an Oregon signee, and 28 points from fellow senior Adrian Mosley, a transfer this season from Grant. The Lions will now play for the LSI championship Friday night at 8:45 against Duncanville of Texas, the top-ranked high school team in the nation.

The Lions missed all 12 of their three-point attempts and trailed by as many as 11 in the first half, but after Mosley dazzled the crowd with a mixtape-worthy exhibition of ballhandling that ended with a finish through three defenders, the supportive crowd began to throw its weight firmly behind the local bunch.

“It was definitely a high-caliber game,” said Mosley, who came to West Linn from Grant along with new Lions head coach Robert Key. “I just honestly fed off the crowd. It’s amazing to be in our city and get them to be on our side like that.”

“That was so amazing,” Key said of the support. “It triggered our kids to play at an even higher level.”

Meanwhile, the Trailblazers from Los Angeles grew increasingly shaky as the fans turned against them. Sierra Canyon led 24-20 through one quarter, and used a 10-3 run to push the lead to 34-23. The Lions outscored the Trailblazers 63-35 the rest of the way.

Shelstad scored the last eight points of the first half to pull the Lions within 40-39 at the break and they received a standing ovation as they left the floor.

“The atmosphere was unreal,” Shelstad said. “We got the whole state of Oregon having our back. The gym was shaking, so they helped us out big time.”

“I told our guys if it was close at halftime, we’re not going to make any adjustments, and we stayed the course,” Key said.

In the second half, West Linn ran the Trailblazers out of the gym, outscoring them 47-29 as oohs and aahs rang out each time Shelstad and Mosley shook their defenders and finished around the rim.

Mosley made 12 of 26 shots from the field, while Shelstad was 11 of 16 from the field and 16 of 18 from the free-throw line.

“Me and Adrian have been playing against those caliber of players most of our lives,” Shelstad noted. “So I mean, we just came into the game confident knowing we could play with those guys, even though they’re a national team.”

West Linn made 30 of 48 shots from two-point range and 26 of 34 free throws. Failing to make a three-pointer seems as if it would have been impossible to overcome against a top 25 national team.

“That wasn’t part of the plan,” Key said with a laugh. “That’s not in our DNA either. But we made them shoot over the top of us and not beat us in the paint too much.”

Sierra Canyon had a major height advantage, featuring several players over 6-foot-6, while the Lions have no players taller than 6-foot-3 in their starting lineup. Still, West Linn outrebounded Sierra Canyon 37-34 and grabbed 14 offensive boards.

Fouls piled up on the Trailblazers in the second half, allowing the Lions to build on a 58-51 lead through three quarters.

“The kids did very well at selling fakes and getting to the free-throw line,” Key said. “I told them at the end of the day that free throws win games, and we’ve been terrific from the free-throw line.”

Starters Mark Hamper, Sam Leavitt and Drake Gabel combined to score 17 points, but provided defensive energy, rebounding and poise under pressure on the offensive end.

Leavitt, Hamper and Shelstad all played for West Linn’s 6A champion football team this fall, and Leavitt is headed to Michigan State next year to play quarterback.

“Having the football players helps,” Shelstad said. “Our team is very competitive and tough.”

Junior Isaiah Elohim, a five-star recruit for the class of 2024, scored 17 points to lead Sierra Canyon. Ashton Hardaway, son of ex-NBA star Penny Hardaway, scored 14 but made just 5 of 16 shots. Bronny James had 10 points in 27 minutes, while young brother Bryce didn’t get into the game. Scottie Pippen’s son, Justin Pippen, scored six points in 10 minutes.

The Trailblazers will have to settle for the third-place game at 7:15 p.m. Friday versus Bishop Gorman of Las Vegas, which fell 83-72 to Duncanville in the other semifinal.

-- Scott Sepich for The Oregonian/OregonLive