TIGARD Four sets of young eyes stare up at Miwako Sakabayashi from chairs at her kitchen table, right index fingers and thumbs fluttering in the air, visions of smooth white beads dancing in elementary-age heads.

Witness the power of the abacus.

"Ready?" Sakabayashi asks, then quickly unleashes a stream of numbers. "Start with seven. Plus one. Minus five. Plus one. Plus five. Minus four. Plus two. Plus one. Minus three."

Brief pause. "How much?"

In chorus: "Five!"

From the mouths of first- and second-graders, the right answer. Without punching calculator keys or scribbling with a pencil. All in less time than it takes visitors to leave their shoes in Sakabayashi's doorway.

At the Japanese Abacus Math School, which Sakabayashi and her husband run from their Tigard home, students use a centuries-old rack of beads and bars to master basic and advanced math skills -- and learn to add, subtract, multiply and divide, quickly, in their minds.

Students and parents praise the classes for building concentration and boosting test scores by making math visual and fun.

Satoko Ehlen of Portland pays $150 per month to send her two sons to study the soroban, the Japanese abacus, with Sakabayashi twice a week.

Several weeks in, the boys are already benefiting. Second-grader Brandon scored 100 percent on his last math test, Ehlen said, and he finished before anyone else in the class.

"The concentration is the key, and they are learning how to concentrate in a more efficient way," she said. "I think it's a great tool for math."

Ehlen, like Sakabayashi, grew up in Japan, where math teachers have used the soroban for more than 450 years. Capable of computing advanced equations, the abacus looks deceptively simple: a series of metal rods run vertically across a wooden frame. Each rod holds five beads, one above a horizontal metal bar and four below it.

Students learn to count on the soroban with just two fingers, starting from the "ones" column in the middle of the frame and moving right to larger columns ("tens," "hundreds,") or left to decimals.

They use their right thumb to move the four lower beads, which each carry a value of one when they touch the bar. The right index finger moves the top bead, which counts for five when it touches the bar.

Students count "two" when two lower beads touch the bar, for example. When one lower bead and the upper bead touch, they count "six." If a lower bead touches in the first column and another touches in the column to its left, they count "11".

Once they've mastered counting -- along with addition and subtraction -- with the beads, Sakabayashi teaches her students to do the same in their heads.

"They can visualize the abacus as if they had it in front of them," Sakabayashi said, "and they can calculate by using their fingers. Your fingers remember."

Her fingers certainly do. Sakabayashi, who has taught abacus in several Portland metro schools and runs the school on top of a day job in the Oregon Health Sciences University cafeteria, can breeze through 20-digit multiplication problems with quick flips of the beads.

"I can't use this," said her husband, Tariq Bukres, pointing to a soroban. "I have to use a calculator. But she is faster than a calculator."

The school, which charges an $80 monthly tuition per child (with a $10 discount for multiple kids from the same family) hasn't added up any profits for Bukres and Sakabayashi yet, but they're not worried.

"Most people don't know what it is," Sakabayashi said. "It takes time to educate people about the abacus."

The handful of students that currently attend her classes have nothing but praise for their teacher.

"It's pretty fun," 7-year-old Brandon said, "because my favorite subject in school is math, and my dad is really good in math, and I want to be maybe as good as him when I'm older."

Brandon's brother, 5-year-old Michael, also takes the class, and his mother called his early progress "phenomenal." But one of the boys' classmates said you don't have to be young to benefit from the soroban.

"It's already helped me add my checkbook up in my mind," said Carman Delano, 49, who drives from Lake Oswego for the classes. "It's amazing for me. I've always been bad at math."