How can I track respondants on an anonymous survey?

I am having students fill out a survey once at the start of the year and again at the end of the year. I would like to keep the responses anonymous but I need to be able to match the first survey responses with the second survey responses to judge effectiveness of the course. I need to be able to compare Student #124's responses at the start of the year to Student #124's responses at the end of the year without knowing who Student #124 is. Is there a way to do this in JotForm?

The easiest way I can think of to do this would be to add a unique ID widget to the form:

https://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form

Then have students use that ID in their final form.  This would require each student to retain a copy of the ID until the end of the class. 

Other than that, I am not sure if there is another way to track submissions anonymously.