带复选框的ng-model在<span> </span>内工作

Question

为什么这不起作用？

 <span class="btn-group" data-toggle="buttons" ng-repeat="team in teams">
        <label class="checkbox btn btn-primary" for="{{team.id}}">
             <input type="checkbox" ng-model="pageData.selection[team.id]" name="group" id="{{team.id}}">{{team.name}}
        </label>
 </span>

但是没有<span的这个工作正常。

    <label class="checkbox btn btn-primary"  ng-repeat="team in teams">
        <input type="checkbox" ng-model="pageData.selection[team.id]">{{team.name}}
    </label>