registro_escolar/templates/login.html

{% block body %}
{% if session['esgallito'] %}

You're logged in already!

{% else %}
<form action="/login" method="POST">
  <input type="username" name="username" placeholder="Username">
<input type="password" name="password" placeholder="Password">
<input type="submit" value="Log in">
</form>

{% endif %}
{% endblock %}