Bootstrap弹出框modal上层的输入框不能获得焦点问题的解决方法

<div class="modal fade" tabindex="0" role="dialog" id="myModal" data-backdrop="static">
 <div class="modal-dialog modal-lg">
 <div class="modal-content">
 <div class="modal-header">
 <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
 <h4 class="modal-title" id="myModalLabel">添加学校</h4>
 </div>
 <div class="modal-body">
 <form class="form-horizontal" name="myForm" novalidate>
 <input type="hidden" ng-model="entity.SchID" />
 <div class="form-group">
 <label for="SchName" class="col-sm-2 control-label">学校名称：</label>
 <div class="col-sm-10">
 <input type="text" required ng-minlength="3" ng-maxlength="30"
 class="form-control"
 ng-model="entity.SchName" name="SchName" placeholder="长度3-30">
 <span class="text-danger" ng-show="myForm.SchName.$dirty && myForm.SchName.$invalid">
 <span ng-show="myForm.SchName.$error.required">名称是必须的</span>
 <span ng-show="myForm.SchName.$error.minlength">最小长度3</span>
 <span ng-show="myForm.SchName.$error.maxlength">最大长度30</span>
 </span>
 </div>
 </div>
 
 <div class="form-group">
 <label for="WebSite" class="col-sm-2 control-label">学校官网：</label>
 <div class="col-sm-10">
 <input required type="url" class="form-control" ng-model="entity.WebSite" name="WebSite"
 placeholder="链接地址" />
 <span class="text-danger" ng-show="myForm.WebSite.$dirty && myForm.WebSite.$invalid">
 <span ng-show="myForm.WebSite.$error.required">姓名是必须的</span>
 <span ng-show="myForm.WebSite.$error.url">链接格式不正确</span>
 </span>
 </div>
 </div>
 
 <div class="form-group">
 <label for="FoundTime" class="col-sm-2 control-label">建校时间：</label>
 <div class="col-sm-10">
 <input required type="number" class="form-control" ng-model="entity.FoundTime" name="FoundTime"
 placeholder="年份" />
 <span class="text-danger" ng-show="myForm.FoundTime.$dirty && myForm.FoundTime.$invalid">
 <span ng-show="myForm.Summary.$error.required">姓名是必须的</span>
 <span ng-show="myForm.Summary.$error.number">请输入数字（年份）</span>
 </span>
 </div>
 </div>
 <div class="form-group">
 <label class="col-sm-2 control-label">入学时间：</label>
 <div class="col-sm-10">
 <div class="selectBox" id="selectMonth"></div>
 <input type="hidden" name="Province" ng-model="entity.MonthList" />
 </div>
 </div>
 </form>
 </div>
 <div class="modal-footer">
 <button type="button" class="btn btn-success" ng-disabled="myForm.$invalid" ng-click="addOrUpdate()">保存</button>
 <button type="button" class="btn btn-default" data-dismiss="modal">关闭</button>
 </div>
 </div>
 </div>
 </div>