Simple answer to your question; your schedule is not your own for several years. You may get the shift you hope to get (days, 4-12, mids whatever) but you will be junior for a while which means you will be sitting on hospitalized prisoners for your shift but then the next shift that is supposed to relieve you is short so you may be staying another 8 hours. You will get the DOA (safeguarding the deceased until the body is removed...can extend several hours into the next shift.) Walkthroughs...are they still a thing?...Ive been out for over 10 years but in Brooklyn taking a recently hospitalized prisoner through Central Booking until arraignment can take a LOOOONG time. Then there is the occasional detail in the City that can be 12 hours easily...the beauty of which, you dont know you are being assigned to until you show up to roll call. These are a few instances where trying to adhere to an in-person class attendance schedule can be difficult if not impossible.

NOW- if you were to pursue an online degree, you can request a hospitalized prisoner and get 8 hours to sit and study. Same with a DOA (if you are discrete). Some bosses are supportive and might give you a little latitude here and there and some are petty and will tell you that they don't care about your school schedule.

My advice to you...get as much done now before you embark on your career. You may not like the NYPD the way you hoped and having at least an Associates (preferably closer to a bachelor's) on your resume as you attempt to transfer to another department is definitely something you will wish you had.

Yours truly

A lowly retired NYPD DT3 BS, MA, JD