$school_list = new WP_Query(array(
'cat' => 4,
'orderby' => 'ID',
'order' => 'ABC'
));
order (string | array) - Designates the ascending or descending order of the 'orderby' parameter. Defaults to 'DESC'. An array can be used for multiple order/orderby sets.
'ASC' - ascending order from lowest to highest values (1, 2, 3; a, b, c).
'DESC' - descending order from highest to lowest values (3, 2, 1; c, b, a).