Maybe I was lucky, but I cannot think of a single part of my PPL that was badly taught.
They cannot teach you everything during the 45 hours, so you're always going to find stuff you don't know/forgot/don't understand/haven't done, but that's not really a reflection on the school (unless it's something in the syllabus or something real important like what to do if there's no oil pressure after startup). It's not bad PPL teaching if they haven't sent me SVFR through the London TMA or given me a cross-channel checkout. Post-PPL all I need to do is find someone and ask. I guess sometimes I have to buy some tea to get them talking, but...