I like your ideas. Unfortunately the variable shows the number of sign-ins (count of detail line) and not the number of students. It seems this simple task is a big challenge in the FRX.

Mon

>It can also be done with Report Variables. Try

>Variable: rnLines
>Value to Store = 0
>Initial Value = 0
>Calculation Type: Count
>Reset At:Group: Student
>
>Variable: rnUnSt
>Value to Store = IIF(rnLines=1, 1,0)
>Initial Value = 0
>Calculation Type: Count
>Reset At:Group: Tutor
>