Main Settings / General Settings/ Student-Parent Portal / Visibility Settings & Rights / Show Contact Details In Classmates Form
This is where you select whether to display classmates contact details to parents/students.
Requires that you have set in “Show Classmates For” in Main Settings / General Settings/ Student-Parent Portal / Visibility Settings & Rights, to “Parent” or “Student” or “Both”.
Example in parents portal
Setting -> Active
Contact details are visible
Figure 1
Setting -> Inactive
Contact details are not visible 
Figure 2