Inside Kate O'Hagan's 4th-grade classroom at PS 97 in Bensonhurst, the law of supply and demand is in full play. Students are manufacturing, distributing and selling their products in their classroom store, as auditors keep close check on the accounts.

Meanwhile, just a few miles away, SallyAnn Bongiovanni’s 8th-grade mathematicians at IS 303 are building suspension bridges and grappling with problems of angles, weight and buoyancy even as they undertake an interdisciplinary study of the history of the bridges all around them and learn about their importance to island dwellers.

The nucleus of all this activity is the presence of a new 3D computer in each classroom.

The computers, which arrived in February, print physical objects from digital data. The amount of material, the rotation of the moving platforms and the design of the object are controlled by the computer’s graphic design software.

O’Hagan says the mechanism is like a thread-and-bobbin sewing machine with a plastic filament or spool used to load the machine.

Emily, the 4th-grade class technician, has her eye on the bracelets the computer is turning out while she trains two classmates to become the next technical team. She is also monitoring stock for the store, keeping track of the supply of combs, nuts and bolts, chains and plastic sharks the computer manufactures, all in a choice of three colors, to meet customer demand.

Class auditors check the customers’ books to make sure they have correctly added what they earned and subtracted what they spent so that they can complete their next transactions at the store. Each customer’s earnings are based on credits earned from other teachers for achievement, good behavior and community spirit.

O’Hagan, who is orchestrating it all, is having the time of her life. She credits the 3D computer with being relevant to just about everything in the curriculum.

“Every chance I get, I go home and think about how else I can integrate it into the curriculum,” she said. “I can’t imagine a better way to meet the Common Core standards.”

The links in the chains made by the computer, she explained, helped explain angles. She has the children create bar graphs to record supply and demand at the store.

The manufacturing process, she said, led to a classroom discussion of the Industrial Revolution. The work with the 3D computer has triggered conversations in class about career fields such as mathematics, engineering and architecture.

It’s no coincidence that 3D computers wound up in the two District 21 classrooms. Both teachers are chapter leaders who met and formed a friendship at a chapter leader training session. Bongiovanni, who admits to a technology obsession, and O’Hagan talked about how a 3D computer would open the door to innovation and new curriculum possibilities, but the cost seemed prohibitive.

But the two women are problem solvers. Inspired by the tech talk at the dinner table among her own teenagers, O’Hagan decided to write a grant for a 3D computer. It was funded through Donors Choose the day she posted it. Bongiovanni followed suit.

In their initial dealings with the new computer, Bongiovanni’s 8th-graders cheered the three-dimensional plastic geometric figures their computer turned out because they were easier to use and understand in their efforts to measure volume than the three-dimensional paper forms they used to create that bent out of shape and fell apart.

As one student pointed out, “These make more sense, especially for kids who are not math whizzes.”

From those simple beginnings, Bongiovanni has moved the class to take on the challenge of “the amazing engineering” of a suspension bridge like the Verrazano-Narrows and “to get a sense of how awesome it is.”

The 3D computer prints the parts that the student teams use to construct their own solid bridge models for a real connection to engineering. They compare their models using math skills to figure out strength and span. Eventually each team’s best designs are incorporated into one imposing suspension bridge.

The two teachers are thrilled to have the 3D computers to enhance classroom learning.

“Our computer is not something esoteric, something just rich kids have,” Hagan said. “Instead it levels the playing field. It’s tremendously inspiring.”