The simplest way is to create a field to store the number of offenses automaticly.
Create a field in your table, name it as suitable, could be r_offender, and in auto-enter - calculated value - insert the instruction Get (FoundCount). Click OK and deselect the box "Do not replace existing value for field(if any)".
Now create a find script to run every time you enter a name, and the field r_offender will be updated according to the found set.
KIDO's suggested solution will, of course, need to include a find that pulls up just the records for the current student in question.
There are any number of other approaches that also work. Feel free to tell us more if this suggestion doesn't make sense or you don't think it works for you.
You can use a portal to display previous offenses data. That depends on your needs and preferences.