AngularJS Error - forms

Question

I got this error in inspector:
Error: [ngRepeat:dupes] http://errors.angularjs.org/1.2.9/ngRepeat/dupes?p0=subject%20in%20subjects&p1=string%3A%D0%90%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%8F
at Error (<anonymous>)
at http://vedomosti/js/angular.min.js:6:449
at http://vedomosti/js/angular.min.js:184:445
at Object.fn (http://vedomosti/js/angular.min.js:99:371)
at h.$digest (http://vedomosti/js/angular.min.js:100:299)
at h.$apply (http://vedomosti/js/angular.min.js:103:100)
at f (http://vedomosti/js/angular.min.js:67:98)
at E (http://vedomosti/js/angular.min.js:71:85)
at XMLHttpRequest.v.onreadystatechange (http://vedomosti/js/angular.min.js:72:133) angular.min.js:84
But I don't understand where my mistake...
I'm writing an application for school. I have table school in MySQL.
With fields:
id, name, 1,2,3,4,5,6,7,8,9,10,11
1,2,3,4... it's classes and they are have information about subjects. Each class have their subjects. Now I'm writing part, in which user can set subjects into classes. 1 to 10 classes all works good. But when I click "load subjects from 11 class", I get this error.
This table with subjects:
div class="large-6 column">
<label>Предметы {{class}} класса</label>
<table>
<thead>
<tr>
<th style="width: 200px;">Предмет</th>
<th style="width: 200px;">Изменить</th>
</tr>
</thead>
<tbody>
<tr ng-repeat="subject in subjects">
<td>{{subject}}</td>
<td><a>изменить</a></td>
</tr>
</tbody>
</table>
</div>
And button for load information other classes:
<button class="button success tiny" ng-click="getSCLASS()">получить</button>
And function for this button:
$scope.getSCLASS = function(){
$http.post("/index.php/panel/getSCLASS", {class:$scope.class}).success(function(data){
$scope.subjects = data;
$scope.s_subjects = true;
});
}
From 1 to 10 classes - all works good. But with 11 class it's not work. I don't understand where my mistake.
Sorry for my English :|

Answer 1

See this and try this:
<div class="large-6 column">
<label>Предметы {{class}} класса</label>
<table>
<thead>
<tr>
<th style="width: 200px;">Предмет</th>
<th style="width: 200px;">Изменить</th>
</tr>
</thead>
<tbody>
<tr ng-repeat="subject in subjects track by $index">
<td>{{subject}}</td>
<td><a>изменить</a></td>
</tr>
</tbody>
</table>
</div>