• Photo gallery: Hawaii Technology Academy

The line began forming before dawn at a drab, mixed-use building overlooking Farrington Highway in Waipahu as parents vied for a chance to sign up their children for a slot at Hawaii Technology Academy.

Just a small white sign tips off passers-by to the location of the fastest-growing charter school in the state, on the second floor above a kayak store and a shredded-foam operation.

"One family came at midnight, and by 5 a.m. we had 51 people waiting outside," said Jeff Piontek, an energetic New Yorker who heads the school, Hawaii’s largest charter. "

Launched in 2008, the public charter school has quadrupled its enrollment over two years, with 1,000 students at last count. On March 1 it opened up 250 more slots for this fall, triggering that line of parents. The school can grow so quickly despite its limited space — 10,000 square feet — because its students work mostly at home. They come to the learning center on average twice a week for face-to-face classes, with additional time for electives.

"It’s one size fits one; it’s not one size fits all," said Piontek, formerly the state science specialist for Hawaii’s public schools. "If you’re a fourth-grader and don’t know fractions, we can teach you. If you don’t know how to conjugate a verb, we teach you. Every child has a customized learning plan."

Students undergo a base-line assessment before they start school. Teachers review their performance every Monday and adjust each student’s agenda for the coming week. The school uses a standardized online curriculum purchased from K12 Inc. Success depends on two factors: an engaged parent and a motivated child.

"Your parent or guardian is actually a teacher; they’re responsible," said middle school teacher Tiffany Wynn. "It’s not sitting your child in front of a computer and saying, ‘Here you go, good luck!’"

Hawaii Tech’s students score well, with 85 percent proficient in reading and 45 percent in math last year. But the school’s close connection with K12 Inc. has raised a red flag with the state auditor’s office, which is examining Hawaii’s charter school system. The for-profit firm gets 41 percent of the school’s allotment of funds from the state. Under its contract, it also pays the principal. That means Piontek is a private employee, not a state employee like other public school principals.

"That is a huge issue with a lot of people," said Piontek, who makes $115,000 a year. "They are afraid the curriculum company is running a public school. I would much rather be a school employee, and so would the local school board."

The board has been trying to renegotiate its K12 contract, which was signed before Piontek was hired and runs until 2014.

HTA enrolls students from South Point on the Big Island to the North Shore of Kauai, some of them competitive surfers or performing artists who need a flexible schedule. The school’s individualized approach has struck a chord, especially with military families and home-schoolers. Piontek pulls up some profile data with a few quick strokes on his laptop: 47 percent of students come from public schools; 31 percent are military dependents; 20 percent were home-schooled; 12 percent came from private schools; 2 percent from other charter schools.

"I could fill the whole school with military, but we want it to be a local school," Piontek said. "Our plan caps it at a third."

Despite the building’s bleak exterior, cheerful posters hand-lettered by students decorate the central hallway, inviting them to join the environmental club or attend a PTSA meeting. An art teacher enlightens her pupils on the concept of proportion at one end of the hall, while biology students dissect rats in its science lab.

"I really like this school because it’s challenging," said Joelle Lee, a soft-spoken seventh-grader with a flair for drawing. "You can work at your own pace. If you get it down in most schools, you have to wait for everyone else. This one, you learn it once and you get ahead and go on to the next thing."