BRENTWOOD -- Chris Bonnie exudes enthusiasm as he works his way around the room of 33 students, correcting, coaching and encouraging at high volume.
Heads bent over worksheets, they tackle a warm-up exercise that challenges them to prove two shapes congruent and calculate the vertex angle of an Isoceles triangle.
Then, without warning, the Heritage High School math teacher dons a pair of reflective sunglasses, slaps a Giants baseball cap on backward, and segues into his alter ego.
"Mr. Bondizzle is back!" he announces.
Pacing back and forth across the room in a crouch, Bonnie launches into a rap.
"Let's get ready for another lesson, I don' want to hear any of your fussin'/The lesson will be about quadrilaterals, the four-sided shapes, boys and girls."
He drives the point home with an off-key refrain as students laugh and train camera phones on their teacher.
"A rectangle can be a square, all rectangles are quadrilaterals/But a square can be a rectangle, this makes math very fair."
"A square can be a rhombus, not a hippopotamus/Rhombus is a parallelogram, not a yummy candy gram."
The mnemonic device works for 16-year-old James Buchanan.
"Last year my teacher just lectured. It was so uninteresting -- I didn't remember any of it," said the sophomore, who's repeating the class. "If we think it's funny, it's easier to remember than just staring at a book."
Jamila Alani, 15, recalls her surprise the first time Bonnie performed his hipster routine.
"I've never had a teacher who raps for me. You get the lyrics stuck in your head," she said, noting that the unconventional tactic has helped her remember the Pythagorean theorem (a2 + b2 = c2).
Bonnie decided to liven up math last year by drawing on his flair for the dramatic, introducing a new topic with a rap act every two to three weeks.
He also routinely plays music before the bell to get students in an upbeat frame of mind at the outset of class.
Snappy hip hop rhythms greet his classes as they trickle in for that day's lesson, ramping up the energy level.
"One two three uh!
My baby don't mess around
Because she loves me so
And this I know for shoo ...."
"You have to find a way to connect with the kids," said the rookie educator who, at 25, almost could pass for a student himself.
Principal Larry Oshodi welcomes the offbeat approach.
"It's always nice to see something fresh, to see teachers use different methods to reach different-style learners," he said.
Integrating music into other subjects isn't unique -- Oshodi has heard of teachers bringing guitars to class or recording voice-overs with a background of classical music or jazz.
The key is not to use the technique so often that the unconventional becomes humdrum and starts to interfere with learning, Oshodi said.
And he has another caveat: "I suspect while many teachers would like to use music as part of their instruction, it helps to be musical ... or bold," he said, chuckling.
But there's more to Bonnie's technique than comedic monologues.
Determined to keep kids focused and motivated, he has them do practice problems that he includes in the daily lesson outline.
"No one's ever sleeping because I am there to push them to do their very best," Bonnie said. "They're always working."
And instead of relying solely on overhead projectors and traditional worksheets, he has students solve problems on their personal whiteboards and hold up the answers so he can see at a glance whether they're grasping a concept.
Bonnie doesn't let up outside class, either.
He tells those who don't do their assignments to see him before or after school to catch up, time that Alani also takes advantage of several times a week to get a handle on the subject that has confounded her for years.
"He makes it a lot easier. He breaks it down and goes into detail," she said.
Bonnie also typically spends about 45 minutes a night talking to the parents of those who are still dragging their feet as well as helping the kids themselves with homework over the phone.
"I want these kids to know that school is important," he said.
To encourage them to continue their education after graduation he made a sign declaring "I AM COLLEGE BOUND" and hung it over the spot where he posts test grades so they're certain to see the affirmation.
It's Bonnie's classroom antics that really make teens sit up and take notice, though.
He got the idea of rapping about math from the 2006 film "The Ron Clark Story," about an idealistic small-town teacher who takes a job in New York City and uses his creativity to inspire underachieving youth the public school system had written off.
Bonnie starts by searching You Tube for video clips featuring instrumental music with a rap beat, then spends several hours coming up with lyrics that rhyme -- at least sort of -- and mesh with the meter.
"It doesn't have to make sense all the time. You just have to make sure you get those math terms in there," he said, acknowledging that it was a challenge finding something that rhymes with "corresponding angles."
After rehearsing in front of his roommates, Bonnie is ready to unleash his muse on students.
"There's things you all have to know, so let's get ready to go/in this world I call math, let's ride that fun quadrilateral path."