Jazz musician Curtis Stigers is deep in conversation with the school's choral group, the Capital Singers, and the Capital High School Jazz band.
The atmosphere is low-key, almost collegial, and not a surprise since Stigers is a Capital alum.
The singers slouch on a riser waiting for their cue. And the musicians are on the opposite side of the stage with brass instruments so brightly shining, sunglasses might be in order.
Or maybe it's just the starshine coming off Stigers. The reaction of the kids to the performer in their midst is a mix of awe and admiration.
"Other than being an amazing musician, he has an amazing gift for being able to share it," says Schuyler Mickelson, who will have a solo later that night in a benefit concert headlined by Stigers.
This is the third concert he's appeared in, a way of giving back and giving a boost to the kids when they need one the most.
"I think we're okay. I think we're good. I just wanted to get a sound," Stigers says to the band.
Then he turns to a fellow sax player who's just finished a brief solo.
"Beautiful, great tone."
Stigers is pacing the stage like a proud dad.
"You all right? You're fine. Because you already played one earlier. You know you can hear yourself. That's the important thing."
A few seats away, senior Jacob Miller is practically pinching himself because it's rare he has a chance to accompany such a gifted performer, and one who's willing to share his ideas.
"He'll talk to our rhythm section," explains Miller.
"He'll say, 'When would you like this to happen? And we'll say, 'Here.' 'Or, how about this?' And it'll be ten times better."
Later in the music room, Stigers sits for an interview and has nothing but praise for the young musicians.
"They're good kids," he says reflecting on the rehearsal. "I've been impressed by how open they are to input. They have a sense of self. They have a fearlessness that I like. But they don't have difficult egos."
Stigers has no ego either, or at least none that's readily apparent. In conversation he's expansive, thoughtful and not as guarded as you might expect.
"I auditioned for the Kiwanis Boys' Band in 4th grade, but the teacher told me I couldn't sing and I should just stick to playing instruments."
He wonders where that teacher is now.
For Stigers, this is a particularly busy moment in his life. He's about to fly off to Copenhagen for a gig with a radio network orchestra.
Then it's back to Boise for a gig with the Boise Philharmonic.
And he's releasing a new album in April.
Heady stuff for the boy who, in the estimation of one teacher, couldn't sing a lick.
In rehearsal he warms up with a cover of the Gershwin standard "Our Love is Here to Stay."
His whisky baritone wraps around the words like he wrote them himself. It's transporting for anyone who knows the classic number. And suggests he could record an album of the American songbook and make it sound fresh.
"On my records, I've covered Beatles tunes, Merle Haggard tunes and Charlie Parker tunes and Duke Ellington tunes," he says. "It's not necessarily where the song is from but where I can take it."
On stage, he slides from a silky growl to a sax solo with astonishing ease and it's clear he's no one-trick pony. And never has been.
But he professes to be embarrassed when he's around the musicians he admires.
"I have a certain style as a saxophonist. I'm a good rhythm and blues sax player, but when the real jazz guys show up, I start scat-singing."
He's good at that, too.
"I study people like Joni Mitchell, as well as Sonny Rollins and John Coltraine. I like blurring the lines between styles of music."
He blurred the lines a few years ago by agreeing to write and record the theme song for a cable TV series that everyone now knows as "Sons of Anarchy."
The music director for the show is a friend and gave him a pitch that even Stigers found a bit odd.
"He says, 'It's about bikers who shoot each other and sell guns and I want you to write the lyric.' I thought, 'Yeah, I can see why you called me. I'm such a biker.'"
But the show's now a hit and helped Stigers reach a whole new generation of fans.
"A lot go to my website and hear my jazz and scratch their heads and say, 'I thought he was a rocker.' Which I am. It's just I also happen to be a jazz singer and a soul singer and a blues singer."
"It's always been my blessing and my curse that I am versatile."