Rails Checkbox boolean values not passing to database

Can't seem to get the checkbox to pass true to my database

this is the middle part of my devise sign-up form.

      <div class="form-group">
    <%= check_box_tag :admin, checked = true %>
    <%= label_tag :admin %>
  </div>

I've set the admin field to default to false in my schema.rb when Null

I don't know where else to start.

If you guys need any screenshots of controllers, etc.

Please comment :)