Checkbox is taking value true for all fields

Here is my code

 <div class="label-container">
        <label><%= t('select_a_prerequisite') %><span class="necessary-field">*</span>:
          <b class="sel-list">
            <%= link_to_function t('all'), "$$('input.list-subject').each(function(checkbox) { checkbox.checked = true; });" %>,
            <%= link_to_function t('none'), "$$('input.list-subject').each(function(checkbox) { checkbox.checked = false; });" %>
          </b>
        </label>
      </div>

      <div class="categories">
        <% @aau_subjects.each do |c| %>
          <div class="each_category">
            <%= check_box_tag "prerequisite[]",c.id, :class => "list-subject" %> <label><%= "#{c.aau_subject_name}  #{c.aau_subject_code} " %></label>
          </div>
        <% end %></div>

In this when i click on "all" , it should make true for all check box, but its not working and checkbox are displayed with default true. please suggest me where i am going wrong , or any other solution for on click true and false.