List Custom Posts Based on Custom Field

Hello, I am using custom press to load in a list of schools. Each school will have a city and state (which I added as custom fields). I want to be able to list out the schools based on what state the user chooses. I am close but I just need some help getting over this hump. I can get all of the schools to display, but how do I filter by the 'state' custom field.

Also what code do I use to display the school's 'city' within the loop? Thanks in advance. Here is the code I have that loops through the School custom posts:

$args = array( 'post_type' => 'schools', 'posts_per_page' => 10 );
$loop = new WP_Query( $args );
while ( $loop->have_posts() ) : $loop->the_post();