Do you need to see the Student ID in any of the tables?
You could create a second field in your data model which is an autonumber or hash of your Student ID field and use this in your tables instead ... you'd still be able to select a student to look at some other information elsewhere in your app, but you wouldn't see the Student ID so wouldn't be able to identify him/her.
Alternatively, you could still create this field, but then have two charts, one with Student ID and one with the second field. You then use a conditional show on the charts to swap them out when an ethnicity or disablility is selected.
This should perform better than a calculated dimension.
Thanks for this.
Yes it's essential that you can see Student number if you haven't selected the 'dangerous' filters Ethnicity/ disability.
The dashboard already uses contitional show to allow the user to switch between coloured (bar etc.) charts and 'Underlying counts' using a button - my problem outlined above occurs in 'underlying' view. I could do a third set of charts with the conditions you suggest. But there are a lot of them! But maybe that's the best solution for optimisation