I have few models - User, Teacher and TeacherLeader.

class User < ActiveRecord::Base                                                              
  attr_accessible ...,
                  :teacher_attributes

  has_one :teacher
  has_one :teacher_leader

  accepts_nested_attributes_for :teacher_leader
end

class Teacher < ActiveRecord::Base
  belongs_to :user                                              
  has_one :teacher_leader
end

class TeacherLeader < ActiveRecord::Base
  belongs_to :user
  belongs_to :teacher
end

I would like to fill TeacherLeader via nested attributes. So, i do such things in controller:

class TeacherLeadersController < ApplicationController
  ...
  def new
    @user = User.new
    @teacher_leader = @user.build_teacher_leader   

    @teachers_collection = Teacher.all.collect do |t| [ "#{t.teacher_last_name} #{t.teacher_first_name} #{t.teacher_middle_name}", t.id ] 
                                   end

    @choosen_teacher = @teachers_collection.first.last unless @teachers_collection.empty? 
  end
end

And also have such view (new.html.erb):

<%= form_for @user, :url => teacher_leaders_url, :html => {:class => "form-horizontal"} do |f| %>
        <%= field_set_tag do %>
            <% f.fields_for :teacher_leader do |tl| %>
              <div class="control-group">
            <%= tl.label :teacher_id, "Teacher names", :class => "control-label" %>
            <div class="controls">
            <%= select_tag( :teacher_id, 
                            options_for_select( @teachers_collection, @choosen_teacher )) %>         
            </div>
          </div>
            <% end %>


          <div class="control-group">
        <%= f.label :user_login, "Login", :class => "control-label" %>
        <div class="controls">
          <%= f.text_field :user_login, :placeholder => @everpresent_field_placeholder %>                 
        </div>
      </div>

      <div class="control-group">
        <%= f.label :password, "Pass", :class => "control-label" %>
        <div class="controls">
          <%= f.text_field :password, :placeholder => @everpresent_field_placeholder %>         
        </div>
      </div>
        <% end %> 

        <%= f.submit "Create", :class => "btn btn-large btn-success" %>
<% end %>   

Problem is that select form here does NOT appear. Why? Do i do something wrong?