获取angularjs中数组的父索引

I have array of scope.students inside the controller. And the data is shown in my view form using ng-repeat in the table. What I want to do now is when I click the button, it should alert the parent index of the specific object. For example I click the button for 1 Brick Med then it should alert 0 because he is in section A. Then when I click the button in 3 it should alert 1 because he is sectionB. I am really new in angularjs any help is millions appreciated thanksI have array of scope.students inside the contr