New Column with count based on Values from two columns

Hi Everyone,

I am hoping this is simple for someone here but I have been having a devil of a time getting the result I need.

Here is my table  

I want a new column that I will call Nr in EG that counts the number of distinct schools numbers within an enrollmen group so the results would look like this

I have measures that give me this count for each enrollment group already but I need a single column that tells me the total number of schools so next to a school i can see the number of schools that are in the same enrolment group.

Any assitance would be greatly appreciated.

Thanks

Kyle

Edit:  Corrected expected output