Django: Passing argument to parent template

There's no direct way to pass a variable up the template inheritance tree the way you describe. The way that people implement navigation bars that highlight the current page is often tweaked to the nature of the site itself. That said, I've seen two common approaches:

The low-tech approach

Pass a variable in the template context that indicates which tab is active:

# in views.py
def my_view(request):
    return render_to_response('app2_template.html', {"active_tab": "bar"},

<!-- Parent template -->
<div id="navigation">
    <a href="/foo" {% ifequal active_tab "foo" %}class="active"{% endifequal %}>Foo</a>
    <a href="/bar" {% ifequal active_tab "bar" %}class="active"{% endifequal %}>Bar</a>
</div>

The higher-tech approach

Implement a custom template tag to render your navigation bar. Have the tag take a variable that indicates which section is active:

<!-- Parent template -->

<div id="navigation">{% block mainnav %}{% endblock %}</div>

<!-- any child template -->
{% load my_custom_nav_tag %}
{% block mainnav %}{% my_custom_nav_tag "tab_that_is_active" %}{% endblock %}

You can pretty much go crazy from there. You may find that someone has already implemented something that will work for you on djangosnippets.org.

Have you tried the {% with %} template tag?

{% block content %}
  {% with 'myvar' as expectedVarName %}
  {{block.super}}
  {% endwith %}
{% endblock content %}