Delaying the answer key would not cause a loss of interest.A couple of days between the test and the keys could actually manage to elicit more participation as well as result in efforts on part of test takers to solve the entire paper solely by themselves, leading to more learning...
Between, the paper was fabulous. Made me realize that I can actually do much much better than I do at present.I need to maintain clarity of thought even when faced with a time crunch.