Created a new model 'klasse' using scaffold, which was pluralised to
'klasses', which I don't want!
Removed all concerning 'klasse' and 'klasses' in the model.
Added inflection "inflect.irregular 'klasse', 'klassen'" to
inflections.rb.
Recreated model again using scaffold.
Did you check all the files created by your scaffold, including the
migrations? Also if you change the inflections, you should restart
your environment (stop/start the server) before they are applied.