<%= form_for([:admin, @age_group_type, @age_group_entry]) do |f| %>
  <% if @age_group_entry.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@age_group_entry.errors.count, "error") %> prohibited this age_group_entry from being saved:</h2>

      <ul>
      <% @age_group_entry.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :short_description %><br />
    <%= f.text_field :short_description %>
  </div>
  <div class="field">
    <%= f.label :long_description %><br />
    <%= f.text_field :long_description %>
  </div>
  <div class="field">
    <%= f.label :start_age %><br />
    <%= f.number_field :start_age %>
  </div>
  <div class="field">
    <%= f.label :end_age %><br />
    <%= f.number_field :end_age %>
  </div>
  <div class="field">
    <%= f.label :gender %><br />
    <%= f.text_field :gender %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

<%= form_for([:admin, @age_group_type, @age_group_entry]) do |f| %>
  <% if @age_group_entry.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@age_group_entry.errors.count, "error") %> prohibited this age_group_entry from being saved:</h2>

      <ul>
      <% @age_group_entry.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :short_description %><br />
    <%= f.text_field :short_description %>
  </div>
  <div class="field">
    <%= f.label :long_description %><br />
    <%= f.text_field :long_description %>
  </div>
  <div class="field">
    <%= f.label :start_age %><br />
    <%= f.number_field :start_age %>
  </div>
  <div class="field">
    <%= f.label :end_age %><br />
    <%= f.number_field :end_age %>
  </div>
  <div class="field">
    <%= f.label :gender %><br />
    <%= f.select :gender, ['Male', 'Female', 'Mixed'] %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

Adjust the way that age group entries see the 'gender' options
Adjust the way that age group entries see the 'gender' options
