You aren't young, so would be going into it with your eyes wide open.
How has age got anything to do with it? 
Unless you have worked as a teacher or closely with a teacher (TA), your eyes are not wide open. Even my DH, who I have been with since my first year of training, doesn’t know everything about my job.
I’m a primary teacher and have strongly mixed feelings about the job. I love working with children most of the time and I love my colleagues most of the time. My partner teacher (assistant head) is amazing and I have learnt so much from her. The additional, non-teaching crap that goes with the job is crippling. I work most evenings and weekends.
As a PP said, it’s awful putting other people’s children before your own but that is often the reality of the job. My DD(6) says she wants to be a teacher and I always tell her to think of something else.
I can’t comment on the degrees needed for secondary but, during my final year of training (I did a BEd in Primary Education with QTS), I had to do a day in secondary. Whilst talking to one of their SLT, I was asked if I’d consider applying for secondary as they had some vacancies. Hell no!!