CodeIgniter - Organizing Controllers into Subfolders
if ($this->user_model->is_user()) {
  // load this controller
}

class Dashboard extends CI_Controller {

function index()
{
  //make a check for the user that returns the usergroup:
  $user = $this->user_model->is_user();
  redirect('controller/'.$user.'/'.$user);
}

}

$hook['pre_controller'][] = array(
                                'class'    => 'Select',
                                'function' => 'get_usergroup',
                                'filename' => 'Select.php',
                                'filepath' => 'hooks');