checkbox that checks only one row in a checkboxes table jQuery

It seems that it's not a big deal but i still can't firgure out the problem: In my razor view I display many checkboxes organized in three columns, and I want to create a checkbox for every row that checks all the row (every 3 checkboxes), so here is what i did using jQuery:

   <table>
        <tr>
            @{
                int cnt = 0;
                string sr =null;
                string j = null;
                List<Security.Models.AssignedRolesVM> Roles = ViewBag.tp_role;

                foreach (var role in Roles)
                {
                    if (cnt++ % 3 == 0)
                    { sr=cnt.ToString();
                      j =(cnt+1).ToString();
                     @:</tr><tr>
                         @: <td><input type="checkbox" id=j  /></td>
                            <script src="~/Scripts/jquery-1.10.2.min.js">
                            </script>
                            <script type="text/javascript">
                                $(function () {
                                    $(j).click(function () {
                                        $('input[name=sr]').prop("checked", $(this).prop("checked"));
                                    });
                                    $('input[name=sr]').click(function () {
                                        if ($('input[name=sr]').length == $('input[name=sr]:checked').length) {
                                            $(j).prop("checked", "checked");
                                        }
                                        else {
                                            $(j).removeProp("checked");
                                        }

                                    });
                                });
                            </script>
                    }
                    @:<td>
                        <input type="checkbox"
                           name=sr
                           class="checked"
                           value="@role.RoleID"
                           @(Html.Raw(role.Assigned ? "checked=\"checked\"" : "")) />
                           @role.RoleID @:  @role.Name
                    @:</td>
                }
                @:</tr>
            }
    </table>

but instead of checking only the row, it does check all the checkboxes. It seems to me that the loop is correct (sr should change every time it is a modulo 3) , any help?