There is a slight problem that I cannot figure out by myself:

I created a custom post type (tours) with custom taxonomy (tour categories). I have created a taxonomy-tour-categories.php to display an archive page for each tour category. Works perfect.

I have a tour category (School tours) which needs a different layout, so I added a second template taxonomy-tour-categories-shool-tours.php with my desired layout. Again it works perfect.

The problem is that the 'school tours' tour category has its own subcategories (like 'workshops', 'science labs' and so on) which I would like to be displayed by the taxonomy.tour-categories-school-tours.php template, but are displayed by the taxonomy.tours-categories.php template. Why that?

I thought that wordpress – when a template file for a specific term is missing – would fall back to the immediately above level template file (in this case taxonomy.tours-categories-school-tours.php). What am I missing?

Thanks for your help!