Ssrs 2012 displayed different data on detail lines based upon a user's selection

In a new ssrs 2012 report, I need to come up with 4 different reports. This is fine since I will have a report parameter and let the user pick what report they want to run. There will be separate tablixes set up with the visibility option saying what report is to be displayed.

However on the third report that will have its own tablix, I need to have different columns displayed when the grade level of the student changes. The data displayed for each school grade level is unique. All the data that will be displayed will fit on one row for each student.
Thus can you tell me how to setup the unique tablix where data will be displayed based upon the grade level of the student?