Model getItem.php

<?php

public function getSchools()
{
	// Get City id for query School.
	$id = $this->getState('city.id');
	
	// Get Admin Model
	JModelLegacy::addIncludePath( JPATH_COMPONENT_ADMINISTRATOR . '/models' );
   	$model = JModel::getInstance('Schools', 'TourModel', array('ignore_request' => true)) ;
	
	// Set Filter, then getListQuery will auto insert into query.
	$model->setState('filter', array('a.city_id' => $city_id));
	
	// getItems
	$schools = $model->getItems();
	
	return $schools ;
}