That is what it is here for.
I did (sort of). I started out as a recruiter. Was promoted to Account Executive for Therapy and Rehab services (same company). From there, became VP of the Home Health division (same company). Got burned out on travel and ended up going to work for a different company in Human Resources, specializing in Employee Relations (eventually taking over all recruiting and staffing).
I didn't go back to school. To be fair, that is because my new role in HR somewhat overlapped with my previous role in Home Health but a lot of it was new to me. I had to do a heck of a sales job in that interview to explain why they should hire me over other dedicated HR professionals that were also in the running. I have a friend that did fraud investigations and then made a complete change to work as a Business Analyst (for the same company). He asked his employer if he could have a mentor, he worked with that mentor for roughly a year, and when a BA position came open he applied and got the job.
I think going back to school is an option if you want to make a career change but it isn't a prerequisite. I don't know what kind of company you work for, but if you can find away to change your role while with the same company you're more likely to not take such a big step back. Whether you go back to school or not, if you decide to go elsewhere you will likely be starting at the bottom + adding on new debt from the recent tuition costs.
I don't know your situation completely but I would caution against making a change just to find something you enjoy more. I think it happens too often where people make a change to be more fulfilled at the work place but now have a the stress of being less financially secure, thus leading to a whole new set of problems outside of the office. Or, they realize they don't enjoy their new career as much as they thought they were going to. There needs to be a happy medium and you also need to look at your future. Where do you want to be in 5, 10, 15 years? Are you married? If not, and you want to be, can you afford a wedding/ring? If you don't have kids, do you want kids? Will this career change make it financially unrealistic to have children? Do you want to travel? Will you be able to save enough to go anywhere? Can you afford your current lifestyle if you took a pay cut?
If the answers are no, the question becomes is it worth giving up some of those things to have a *potentially* more enjoyable job? I say potentially because the grass is not always greener.
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Those are my thoughts.