Well, I had to stop and think a bit about this one. On reflection, I realise I've had hardly any formal teaching, apart from practical flying!
When I got my PPL, 35 years ago, I was training in ATC, and it was assumed that the legal side, navigation, plotting, and Met. were covered there. We received probably about an hour of aerodynamics, and had a 10 question multi-choice written test (I think). We had to pass a separate R/T "airborne" exam, but that was pretty simple.
The rest was practical flying, including spins and cross country. I missed out on crosswind landing for some reason (still evident now!

). There was no instrument training at all. Minimum qualifying time was then 30 hours - that's exactly what we got - 30 hours and a PPL!
When I regained my PPL some 35 years laer, it was all self study with Trevor T. , the Confuser and MS2002 for instrument training. Regaining the licence was about 25 hours of flying and no ground school (averaged 95% in the exams though

). I had 30 minutes of instrument flying ground school and about 90 minutes of instrument flying before the skill test. Here's to MS2002

.
So its kinda difficult to say which was the worst, since whatever it was it must have been me.