[ZeroGravitas]

I think you are confusing O-levels and A-levels. O = Ordinary, A = Advanced, generally people going on to University would do A-levels, so leaving to get a job with only O-levels might be roughly equivalent to having a High School Diploma I think.

[walshemj]

Think professional apprentice / associate professional entry point.

Now a lot of jobs that where available to school leavers are graduate entry - talk about grade inflation :-)

[hga]

Oops, you're right!

So change O -> A in the above, and O-Levels in the Potterverse correspond to OWLs.