A bachelor's degree in education is going to be perceived by med adcoms as "weak" compared to a degree in biology, chemistry, math, or even history or English. If you want teaching to be a back-up, major in whatever you'd hope to teach and do your pre-reqs. If you decide you want to teach, you can get a job in a private school (I even had a med student who taught in a private English language school for ex-pats' kids for a year or two before med school.) or do Teach for America which will get you a provisional license to teach for 2 years while you earn your master's degree in education on the side. The typical path is to apply to medical school during the second year of the two year TFA gig. If you decide that you love teaching, you can continue down that path with your teaching license courtesy of TFA. Or you may find something entirely more appealing than either teaching or medicine.