Для другой структуры ДИВов...
<!DOCTYPE html>
<html>
<head>
<meta http-equiv='Content-Type' content='text/html; charset=windows-1251' />
<script src='https://code.jquery.com/jquery-latest.js'></script>
<!--
<script src="https://code.angularjs.org/1.3.9/angular.min.js"></script>
<script src="https://code.angularjs.org/1.3.9/angular-route.js"></script>
-->
<style type='text/css'>
</style>
<script type='text/javascript'>
$(function(){
$('.10 .11').each(function(){
$(this).parent().find('.12').removeClass('12').addClass('13');
});
});
</script>
</head>
<body>
<div class='10'>
<div class='11'>
</div>
<div class='12'>
Ok
</div>
</div>
<div class='10'>
<div class='12'>
No
</div>
</div>
</body>
</html>