I think this concerns money more then making a choice.
1. If you can afford a degree study, then attend the assessment
but tell them Prisons no thank you. You want to finish your degree
and join as a SO later.
Even if you are not selected for your degree class, that gives
you a few more months to work at getting into the classes.
You can be working in part time jobs or in some cases, make use of
your diploma, even if its for a few months.
2. If it was a matter of generating income to support your
Degree Class, then please tell them no thank you. Because
unless you choose to do your degree class maybe two years after
your sign on, or you do it part time two years after you signed
on. You are looking at from paycheck to mouth kinda
situation.
Either way, both are because you wish to persue further
studies. Not because you wish to join the prisons due to any
higher calling. Then I rather you focus on your priority,
which is your degree.
Dont think part time studies is going to be easy. Not
unless you have been working a while and studying part time for the
last 3 years.
But then, I dont know you. Who knows......you might
just be able to juggle those responsibilities.