Rails 4 not changing post method to patch

Question

I am trying to submit a form, but if I just put form_for @classroom I get a \"No route matches [POST]\" error.

Now with the code posted below, I get th

Answer 1

To add a bit of specificity, to Tashow's answer above (which set me on the right track), I had some hidden fields that look'd like this, in a nested form.:

<%= hidden_field_tag("Classroom[classroom_teachers_attributes][]", nil) %>
<%= hidden_field_tag("Classroom[classroom_teachers_attributes][]", '') %>

Once I got rid of these, everything began working properly again. (There still remained similar-looking tags generated by fields_for, etc.)