I have some experience in this topic. Private school faculty members in this area generally are paid starting salaries of about $30-34 k (public tends to start at $40-46 k, with an average bump of roughly 7.5% for further education). Under most circumstances, interim state licensure is required for publics by the end of the second FTE year or the third year, if the position is licensed. Note that many private school teachers are considered "part time" when starting, are paid proportionally less, and receive few if any employee benefits especially when part-time.
With five to seven years' seniority, a public school teacher in this area generally received about $58-70 k. A senior teacher in the Arl, DC, Alex, or MontCo system (more than a dozen years FTE) generally sees 75+ (again, with an average bump of roughly 7.5% for further education). There are sometimes further bumps on the pay-step system, but in many local divisions, steps over the 10 or 12 year point are discretionary and performance-based. The Alex system is about average for the region, and you can see the scales here:
http://www.acps.k12.va.us/hr/compensation/
Teachers in public systems in DC, MD and VA, when full-time, must also receive at least minimum pension coverage, which adds relatively significant value to the compensation package. They also receive health, life, accident, and long-term disability-income insurance (except in DC, where long-term disability income insurance is factored into the pension system). At most private schools, partial premium payment for health insurance is the only available benefit. At some private religious schools, there are significant further limitations on benefits.
Social workers/psychs, specialists, and fully RN-licensed school nurses generally are paid on the teacher comp systems. Principals are generally at materially higher grades or on their own higher pay steps.