In the U.S., preparation to teach in public schools is strictly overseen by state education departments. For that reason, rules governing the substitution of work experience for academic credit vary greatly from state-to-state. In addition, colleges may apply an additional layer of rules regarding such credit transfers, so applicants should carefully review each school's requirements.
If you want to teach high school, states require you to have some expertise in the field you intend to teach. Whether you are going after a single subject or multiple subject credential, previous professional experience can come in handy. For example, a chemist aspiring to teach chemistry may be able to waive some of the subject area training for that degree. That said, even an experienced chemist (or one with an advanced chemistry degree) will still need to take teacher preparation courses, state exams, and go through a supervised or student teaching practicum.
If you've taught before, you may also be able to forgo a chunk of your teacher training. These days, most teaching degrees have a hands-on component in which students either teach or observe experienced teachers in a live classroom. In California, private school teachers with three to five years of full-time teaching experience can waive this student teaching portion of the degree program, provided they taught at regionally-accredited private schools and came away with positive evaluations. Instructors with six years of experience may be eligible to waive both the student teaching and the teacher preparation program. (Don't forget, individual institutions may decline to allow such waivers.) New York offers similar waivers and Florida accepts college teaching as a replacement for portions of its degree programs.
Links to teacher certification requirements in all 50 states are maintained on the University of Kentucky's website.
Teachers who already possess a teaching certificate or license from another state may be able to avoid a degree program entirely. Most states permit transfer of a teaching license or certificate from another state, provided that state's license or certificate requirements are similar to the target state. Where differences exist, additional training may be required.