How to get the difference between the values selected by slicer?

Hi all,

I am new to Power BI and currently I am working with table visulaizations and slicers. 

My data is as follows

Student table:

Date table:

Exam table:

I want an output like the image shown below,  I would like to create 2 table visuals that can be filtered on Student Name, Classroom and also have slicer on 2 dates. I need to compute minimum score. The user must be able to select 2 dates at a time on the slicer, the first date selected on the slicer should be attached to my 'Min Score at date1' and second date selected on the slicer should be attached to my 'Min Score at date2', and the third column 'Difference in Score' must be able to calculate the difference between the Min Score at date1 and Min Score at date2.  

Similarly I also want to calculate the average minimum score too

Please let me know how to proceed or what alternative formula or method should I implement to get the desired result.Thanks!