Forms 角度误差

我在inspector中遇到了以下错误：

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

从1到10节课-所有课程都很好。但是有11节课，这不是工作。我不明白我的错误在哪里

对不起，我说的是英语：|

请查看并尝试以下内容：

<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>

Паааааааа
Предмет
Изменить
{{subject}}
изменить

<button class="button success tiny" ng-click="getSCLASS()">получить</button>

$scope.getSCLASS = function(){
        $http.post("/index.php/panel/getSCLASS", {class:$scope.class}).success(function(data){
            $scope.subjects = data;
            $scope.s_subjects = true;

        });
    }

<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>