get multiple count selected

I need to count teacher_id selected.

my input:

<select class="js-example-basic-multiple" name="teacher_school_id[]" id="teacher_school_id" multiple="multiple" style="width: 100%;">
<?php foreach($teachers as $teacher){
?>
<option value="<?php echo $teacher->teacher_id; ?>"><?php echo $teacher->teacher_name; ?></option><?php  } ?></select>

div:

<div id="test">Here i need how many teachers are selected</div>

script for counting teachers:

$(document).ready(function () {
$('#test').html('How many teachers?: ' +0 + ' entries');
$('.js-example-basic-multiple').change(function () {
    var count = 0;
    $('.js-example-basic-multiple').each(function () {
        if($.trim($(this).val()).length > 0)
            count++;
    });
    $('#test').html('How many teachers?: ' +count + ' entries');
}) 

script for multiple selection:

$(document).ready(function() {
$('.js-example-basic-multiple').select2(); 

But still doesnt work. No count. No output displayed. Any suggestion? Thanks a lot.