An at a glance "How many schools are reporting" on the applied dataset.

Without looking at the school overview and counting the number of schools included, users wont realise that potentially NOT all schools are included in the measures; as most users will not have data management permissions to see.
A good place to show this would be next the the "No filters applied" section as that is viewable on all levels. The data could be picked up from the Data Management sections for reports that are enabled to view.