app/views/teachers/_form.html.erb
<h4>Add a new teacher</h4>
<%= form_tag :organization_teachers do %>
<%= render 'shared/error_messages', target: @teachership %>
<div class="form-group">
<%= label nil, :email %>
<%= text_field_tag :email, nil, class: 'form-control' %>
</div>
<div class="actions">
<%= submit_tag 'Add a new teacher', class: 'btn btn-primary' %>
</div>
<% end %>