Sitting at a sewing machine, Carlsbad High School senior Jeremy Bullara displayed a black nylon dog collar, and explained some simple business math. The collar, made from upcycled climbing ropes, also reduces waste and offers students hands-on experience in running a small business, through their Virtual Enterprise class. The class is part of a program in which students interview for jobs, create business plans, manage budgets, develop virtual products and compete against other schools. Most campuses that offer the program run entirely on a virtual basis, creating and marketing hypothetical, digital products. Students at Carlsbad, however, manufacture and sell real goods that they produce during spring semester. One section of the class runs Project EcoPaws, which manufactures pet collars, leashes and harnesses from used climbing ropes donated by climbing gyms. The other team, GEA Jewelry, creates resin earrings, necklaces and bracelets with recycled, expired cosmetics. “We take the makeup waste that people would throw away,” said Ember Sierra, 17, a junior at Carlsbad High. “We put it in eco-friendly resin, and then we put it in molds and put it in jewelry.” Sierra pointed out...