L.H.
Don't through the baby out with the bathwater. If you are good at what you do and like it, don't toss your career just because you've encountered one employer who focuses only on the hours on your timesheet.
When I came back to work after maturnity leave, my boss (a woman) told me she expected me to work 60 hours a week (by the way, the standard work week at that employer was 37.5 hours), something I was not prepared to do. I was ready to chuck it all in and go back to school, but financially that was not an option for me.
Speed forward four years. I stayed in the same career, but focused on finding a job in a company (and with a boss) with a culture that advertized and practiced work life balance. I believed I could find such a job (key) and, after really focusing time and energy on that job search (seeing the time spent on the search as an investment in me and my family), I found a job that offered better balance and a much more supportive work environment (oh, yeah, and a payraise).
Also keep in mind that you may not need to return to school to change careers. You probably have a host of transferrable skills and it could be just a refocusing of your resume or a short certificate program (e.g., 2-3 hours once a week for 6 weeks) that could help you shift careers or focus.
Whether changing jobs or careers, remember that it typically will take a lot of time and energy to accomplish and typically we only discover the need for this change during a time when there are so many other demands for your time and energy. Be kind to yourself. Be sure to surround yourself with support (husband, family, friends), stay focused on the goal and follow-up with a "cheerleader" when you get discouraged.
Best of luck on whatever you decide. And don't allow yourself to be treated terribly.