The octopus was not cooperating.

Instead of writhing about in its tank, demonstrating for the assembled students its size and movement patterns, the Shedd Aquarium's giant Pacific octopus was just kind of sitting there, up in a corner, a row of tentacles pressed against the glass.

And in the adjacent tank, two Japanese giant spider crabs appeared to be jousting for space, a quasi-science fiction spectacle that was pretty hard to resist.

"Hey, look, buddy's getting knocked out," said one of the boys, an eighth-grader at Carter School of Excellence in the Washington Park neighborhood.

Still, most of the students stood in front of the octopus, along with two Shedd learning specialists, and tried to figure out whether the enrichment tools they had crafted for the animal would work. It is one thing to come up with a little boxlike puzzle that would contain a treat such as food or ice in the lab; it's another to see it in front of the animal.

"What would go in these holes?" said Brandon Pope, one of the Shedd staffers, holding up a 3-D printed plastic device that looked like something you might find in a cereal box. "How would they get it out?"

One girl thought her group's device was too small. "They might eat it," she said.

Another thought her tool was just right. "It's the perfect size," she said.

This was the last of 10 after-school sessions for the first group of middle schoolers to participate in the aquarium's Club Shedd program, which has been bringing in 60 high school students a year for an intensive Shedd experience.

During the weekly sessions, the fifth- through eighth-graders from Carter had learned about existing octopus enrichment tools, met the animal, then designed their own concepts on paper, in clay and then in a computer-aided design program before seeing them constructed on a 3-D printer. The most promising of them will be presented to the aquarium's fabrication team for possible incorporation into the octopus enrichment program.

"What it's given them is an open place to throw out creative ideas," said Sara Jacobson, a fifth-grade math and science teacher at Carter who has accompanied the students most weeks. Instead of the more disciplined school environment, "they just had to have a vision and a defense of why it would work."

Also invaluable, according to Jacobson: "The authenticity" of seeing various Shedd staffers at work. "This just puts so much ground beneath them. This isn't fairy tales. This is a job. 'This could be what I choose to do.'"

The program came about through a partnership with Citizen Schools Illinois, which is also in the enrichment business. It provides expanded learning to Chicago Public Schools middle schoolers, with an emphasis on the STEM disciplines.

"We find our kids, they aren't going to the museums downtown," said Jeanette Castellanos Butt, executive director of Citizen Schools Illinois. Exposure is key to addressing the "achievement gap" between high- and low-income students, she said: "It is not enough just to do academic remediation."

Meanwhile, she said, "kids love any apprenticeship that gets them off campus. And this one is extremely hands-on and engaging."

The range of skills involved in designing an octopus toy was not lost on the students, many of whom worked with CAD and 3-D printing for the first time.

"This helps me prepare for a future in engineering," said Sebastian Bruner, 14, an eighth-grader. "At first I thought it was going to be boring, but I actually made extra time for this."

Another Sebastian, 11-year-old Sebastian McIntosh, sat in a Shedd classroom, preparing a presentation he will give about his experience.

"What makes my design special," he said, "is that it's cylinder-shaped so when it reaches its tentacle in, it won't get stuck."