I want to validate two columns together wrt uniqueness

Validate uniqueness of two columns in Laravel.

controller

function insert(Request $request)
    {       
    $this->validate($request, [
     'School_name' =>  'required',
     'class'       =>  'required',
     'Address'     =>  'required|composite_unique:School_name,Address',
     'Country'     =>  'required',
     'State'       =>  'required',
    ]);

via Chebli Mohamed