public function deletegroupAction()
 {
     $groupID = $this->_request->getParam('g');
     $group_DB = new Application_Model_DbTable_Group();
     $student_DB = new Application_Model_DbTable_StudentsInField();
     $students = $student_DB->getAll($groupID);
     foreach ($students as $s) {
         $data = array('groupID' => NULL);
         $studentID = $s['id'];
         $student_DB->update($data, "id = {$studentID}");
     }
     $group_DB->delete("groupID = {$groupID}");
     $this->_redirect("/managegroups");
 }