wanting to quit job?

So I started working for a daycare in March so I could just get out of the house and have social interaction after my son was born. When I took the job my hours were 9-6 and I was getting off on time and now my hours are 7:15-4:15, but I never get off at  4:15! I always end up staying until 5:20 or 5:40 and I work Monday-Friday. I was lead to believe I would be getting off on time and that's not the case.  Apparently from talking to other employees it has always been that way where no one has gotten off on time. Yet other employees come into my closing room and leave me over ratio dropping off two kids so they can leave on time. I don't do that because I don't feel comfortable. Plus I would probably get in trouble. I'm just pretty fed up. I drop my son off at a babysitters (I pay by the hour) house and 6:40, so I can to work by 7:00 and I usually don't get to him until almost six! That is 11 hours with a sitter. That is a long time. It would be a little different if I was getting off on time. I said something to my boss and she just said I know I'm trying to hire more people. It's been this way over 3 months. I just want to quit and l'm really bad at confrontation and don't know what to say to my bosses.