my students keep taking these tests more than once

[Mark Klune]

I'm enjoying Forms to create assessments for my students, but I haven't figured out how to stop them from taking the tests more than one time.  It distorts the data I'm collecting.  Is there a way to limit the number of times users can submit their answers?

[#2]

If you require authentication ("Only people in my organization") there is a sub-preference under that to "Allow only one response per person" optionally.