I have a form with checkboxes that works fine, but when the user submits the form with errors and my checkbox is checked I need to change div class which holds the checkbox. So
While, first you should use BooleanField in your model, not the CharField. Then, there are two accesses:
just put {{form.yourField}} in your template (preferred)
or, use {% if form.yourFiled.value %} checked {%endif%}