Mask or change a value of a report or chart when below a certain threshold.

I need to be able to mask\change\hide the value returned by a measure IF it have fallen below a certain point.

We create reports that show proficieny of students at schools. These reports include the ability to break groups down by race, gender etc. The problem is we don't want to show anyone a count that is so low that it could identify students within the report. For example lets say a school has 5 Asian students, if the count of proficient students were to fall below 10 (which it would in this case because there are only 5 possibly proficient students) I want to show "< 10" or "less than 10".

This would help us maintain student confidentiality as we try to provide our reports in the aggregate.