This is old anecdata, but as someone who taught at the CalState system in non-entry technical courses (so most outright failures already washed out before me):

1) 4 year students had my best average, but also my widest standard deviation. My best and my worst students were in this group.

2) Community college transfers had a slightly lower average than my 4 years, but the standard deviation was a lot tighter. They were optimizing time and schedule.

3) Returning professionals had an even slightly lower average than CC transfers, but the standard deviation was super tight. They mostly targeted the low end of the B grade range. They were very strongly optimizing every ounce of their time schedule.