TabBar _getTabBar(List<Student> students) {
  var tabs = _getTabs(students);
  if (_tabController == null)
    _tabController = TabController(vsync: this, length: students.length);
  _tabBar = TabBar(
    labelColor: Colors.white,
    tabs: tabs,
    controller: _tabController,
  );
  if (students.length == 1) _tabBar = null;
  return _tabBar;
}

@override
void dispose() {
  if (_tabController != null) _tabController.dispose();
  super.dispose();
}