Chances are that you don't have the data sorted by School.
This is a many to one mail merge.
Modify the document as attached and download
http://www.gmayor.com/ManyToOne.htm re-attach the data source and set the merge type as Letters.
Sort the data by the School field. School is thus the Key field. The fields LastName, FirstName and Decision are the Child fields.
You can then produce your letter in a variety of ways.
If you want the contact field inserted as a hyperlink then see also
http://www.gmayor.com/hyperlink_merge_fields.htm