Here's what I would do. If it's not a very long distance from school to home, I'd wrap the incubator in a blanket so it doesn't lose any heat, carefully transport it home for the weekend so you can manually turn the duck eggs, then bring them back on Monday. If you don't feel that that's a possibility, maybe you can see if someone has an incubator you can borrow to use as a hatcher for the chicks. Or, you can just not turn the duck eggs for the weekend. Not ideal, and it may not work, but that might be your only option.