$schedule= new WP_Query( array( 'post_type' => 'schedule' ) );
if( $schedule->have_posts() ) {
	while ($schedule->have_posts()) {
		$schedule->the_post();
		the_title( '<h1>', '</h1>' );
		$temp_post = $post;
		$workshops = new WP_Query( array('post_type' => 'workshop') );
        if( $workshop->have_posts() ) {
       		echo '<ul>';
			while($workshops->have_posts()) {
				$workshops->the_post();
				the_title( '<li>', '</li>' );
			}
			echo '</ul>';
		}
		$post = $temp_post;
	}
}