I showed this post to my husband, who is a high school assistant principal, and has his B.A. in English, M.Ed. in Education, and M.Sc. in Educational Leadership. He's seen LOTS of teachers burn out in a hurry, so he didn't agree with the idea of going directly into education from nursing.
The problem with so-called "need" or "leave-replacement" certification, which is where you go directly into the classroom without receiving your teaching certificate, is that you are pretty much thrown to the wolves. States that permit this sort of certification usually do so b/c of a shortage of teachers in the science and math fields. The burnout rate is extraordinarily high among CERTIFIED first-year teachers, and those teachers have had the training and know what to expect. Our marriage almost didn't survive Tom's first year of teaching; for every hour you spend in school, you spend at least another at home, creating lesson plans, grading papers, and doing other administrative tasks.
Tom recommends that you check out your local university for fast-track certification options. In Tom's case, he did a two-year M.Ed. programme, where he earned both his Master's and his teaching certification. The certification gives you both mobility (most states have reciprocal licencing) and the education in the minutiae of teaching--lesson plans, classroom management, etc.
One of the teachers at his high school is a former attorney, and another is a former critical-care RN, and both of those teachers completed their certification with their Master's in education and have done very well.
On the topic of private schools, you should know that in most cases the pay is lower and the parents more demanding--this is why they accept non-certified teachers. In addition, in most states, experience in a private school classroom does NOT count as classroom hours toward a teaching certificate. Tom interviewed at several private schools prior to his first year of teaching, and was not impressed.