You buy a clock that costs $78. You pay with a $100 bill. How much is your change?

The group of second-graders presented with this problem last month at Leclaire Elementary School in Edwardsville, Mo., didn't immediately grab their pencils and subtract 78 from 100.

Instead, they grabbed their "number charts." A minute later, hands shot up.

Teacher Carol Peterson called on student after student, asking, "How did you figure out the problem?"

When Armani went to the board to show his classmates, he counted on his chart by 10s from 78 to 88 to 98, and moved over two "ones" to reach the right answer, 22. Peterson complimented him by saying, "I like your strategy."

It's called Everyday Math — a reform curriculum developed by the University of Chicago in the 1980s and now used by nearly 3 million students throughout the United States.

Its hallmark is its emphasis on encouraging students to use different strategies to solve problems, instead of one standard way. The program also "spirals" instruction — introducing a topic, then returning later to master it. Everyday Math introduces concepts — like algebraic variables, geometry and measurements — early. The program also urges students to use "manipulatives" or tangible items, like cubes or cards, to solve a problem or master a concept.

But its nontraditional focus may also mean that parents of elementary children are mystified by the way their children are completing multiplication, addition, division or subtraction problems.

For example, a child adding 326 to 575 would first add the hundreds column, then the tens, then the ones, then add up the results — a foreign strategy for many adults.

"I've wanted to throw the math book into the driveway about five times," said Stephanie Louvier, whose fourth-grader, Jordan, is a student at Blackhurst Elementary in St. Charles, Mo. "I have to learn it right along with him."

Local schools have sponsored "math nights" to help parents become acclimated to the program. Teachers send home family letters at the beginning of the unit to explain what's coming.

In some states, the "math wars" over programs like Everyday Math vs. traditional math have parents complaining that their children are frustrated with the pacing and that they should be studying the traditional algorithms.

Many academics agree, saying programs like Everyday Math will leave children woefully unprepared by focusing too much on hands-on exercises instead of drills and practice. J. Martin Rochester, a professor at the University of Missouri at St. Louis, cautioned in an op-ed piece in the Post-Dispatch that the program placed too little emphasis on the basics.

Some parents at first complain about the "spiraling" — that the teacher moved on before their children had mastered the concept and that instruction jumped around too much.

For example, a first-grade text may touch on tally marks, then jump to time and money. It looks like a "discombobulated bunch of muck," but all three topics deal with the concept of bundling into fives, said Jan Keenoy, Clayton, Mo.'s elementary curriculum coordinator

"I think many of the critics still see math as needing to be taught formally in compartments," she said.

Carol Peterson, who has taught second grade at Leclaire Elementary School in Edwardsville for 29 years, was skeptical in 2001 that her second-graders could grasp some of the concepts in the new program. She knew the program was selected because it closely mirrored state standards for math, but she and others were nervous, she said.

Now, she loves teaching math.

"I think the children truly understand math instead of just memorizing it," she said.

She sees in some of the lessons for her second-graders the groundwork for algebra and geometry.

Rob Canada, a fifth-grade teacher at Columbus Elementary in Edwardsville, knows some of his students' parents aren't thrilled with the methods. But to him, the traditional way worked only for people who could jump through the hoops. And the spiraling that so many hate allows more students to master the concepts with repeat exposures, he said.

His school Web site shows dozens of pictures of students playing games that teach fractions, probability and polygons.

"I have no doubt that this is the way to do it," he said. He noted that more than 90 percent of Columbus students met or exceeded state math tests.

Keenoy said she knows that a significant number of people nationwide think Everyday Math is horrible. She monitors the math wars, reading the criticism online.

"We want to make sure our bases are covered, that we see what the criticism is," she said. "We are constantly monitoring the data and asking ourselves, 'Is this working for our students?'" she said.