ajax stopped working when not logged in?

Have had an autocomplete field working for months but has stopped working when not logged in? Not sure when but within the last few days or week (not updated wordpress recently).

already have;
add_action(‘wp_ajax_filter_schools’, ‘filter_schools’);
add_action(‘wp_ajax_nopriv_filter_schools’, ‘filter_schools’);

in functions.php and there are no errors anywhere.

response i get when not logged in is;
from safari…
*Request URL:http://www.payingforit.org.uk/wp-admin/admin-ajax.php?term=holywe&action=filter_schools&postType=school
Request Method:GET
Status Code:302 Found*

any help welcome ! Dc.

jquery code

 $( "#userSelectedSchool" ).bind( "keydown", function( event ) {
            if ( event.keyCode === $.ui.keyCode.TAB &&
                    $( this ).data( "autocomplete" ).menu.active ) {
                event.preventDefault();
            }
        }).autocomplete({
            source: function( request, response ) {

                $.getJSON( "/wp-admin/admin-ajax.php", {


            term: extractLast( request.term ), action: 'filter_schools', postType: 'school'
            }, response );

            dataToBeSent = {
                term: extractLast( request.term ), action: 'filter_schools', postType: 'school'
            }

            console.log(request.term);

        }, select: function( event, ui ) {

            var terms = split( this.value );
            // remove the current input
            terms.pop();
            // add the selected item
            terms.push( ui.item.id );
            // add placeholder to get the comma-and-space at the end // ui.item.label
            terms.push( "" );
            this.value = ui.item.label;

            $('input[name=userSchool]').val(ui.item.urn)

            return false;

        }, open: function() { $('.ui-menu').width(300) }

});

function in functions.php

add_action('wp_ajax_filter_schools', 'filter_schools');
add_action('wp_ajax_nopriv_filter_schools', 'filter_schools');

function filter_schools(){
    global $wpdb; // this is how you get access to the database

    $str = $_GET['term'];
    $action = $_POST['action'];
    $postType = $_POST['postType'];

    $finalArgs =  array (
        'posts_per_page'=>5,
        'order' => 'ASC',
        'post_type' => 'school'
    );

    $searchSchools = new WP_Query( $finalArgs );
    $mypostids = $wpdb->get_col("select ID from $wpdb->posts where post_title LIKE '".$str."%' ");

    $args = array(
        'post__in'=> $mypostids,
        'post_type'=>'school',
        'orderby'=>'title',
        'order'=>'asc'
    );

    $res = new WP_Query($args);
    while( $res->have_posts() ) : $res->the_post();

        global $post;

        $EstablishmentNumber = get_post_meta($post->ID,'EstablishmentNumber', true);
        $URN = get_post_meta($post->ID,'URN', true);
        $add = get_post_meta($post->ID,'address', true);

        $schl = array('post_id'=>$post->ID,'id'=>$EstablishmentNumber, 'label'=>$post->post_title.', '.$add['town'].' '.$add['postcode'] , 'value'=>$EstablishmentNumber, 'urn'=>$URN );
        $matchedSchools[] = $schl;

    endwhile;

    echo json_encode($matchedSchools);
    wp_reset_postdata();
    die(); // this is required to return a proper result
}