I often found those with degrees were far more difficult to train than those with just O and A levels. As Andy says, they didn't have the underlying keenness and interest as an enthusiast.
I knew a FISO who was 'ace' with about 6 in the circuit and others leaving and joining, but he only had 2 O levels, so couldn't even apply to become an assistant in NATS. I suppose the RAF would have took him, but service life doesn't suit everybody.