I used this simple tracker this year to help make sure I was rotating student jobs appropriately. I had 18 students and 10 jobs, so students had some sort of job every other week.
I would look across each row to see who hadn't done that particular job in awhile. Since I was using the students' numbers, instead of names, I found it easier to quickly spot who needed to go where for the upcoming week. Sometimes I would sit and do a whole month in advance and then I wouldn't have to worry about it for awhile - a nice treat!