It's up to every school to decide what qualifications to require. It's a free market out there, so much depends on the supply and demand situation at the particular location.
Obviously, the schools in popular countries receive a lot of applications so they tend to be picky. For example, the American school of Barcelona requires a MA for every teaching position.
Most international schools are happy with the following:
A four-year bachelor's degree
Teacher certificate from your state / country
Two years of full-time elementary or secondary school experience
A two year commitment
Certification is not always required, especially if you have substantial experience in your teaching area.
Important. Schools can only legally hire those who meet the country's work visa requirements. They usually include teaching credentials, education and age. For example, Turkey requires that all teaching candidates be certified, regardless of the position.
Note, that many schools in the EU will not sponsor a visa unless they can't find a suitable candidate from within the EU.
What teaching areas are in demand?
All those with experience in the IB programmes - PYP, MYP, DP. If you are not familiar with the IB, go to the IBO website to familiarize yourself.
Secondary (A-Level / AP / IB DP ) Biology, Chemistry, Physics, Math, Computers, Music and Library Science. The certification requirement may be waived for these teachers.
Most frequent: Elementary / Primary Classroom educators, as well as English teachers, at various age levels. These positions are abundant all over the world.
MA is required.
You must have substantial experience (more than 5 years) and excellent references.
Oftentimes, knowledge of a foreign language is expected.
International experience is desired.
The competition for administrative jobs is substantial. The schools prefer administrators with overseas experience and full certification.
The school boards look for experienced international leaders who are familiar with the accreditation process, the IB curriculum, international recruitment, fundraising, cross-cultural networking and who can operate in a foreign environment (bilingual).
You have to be prepared for a global search and tough competition. You are not in the position to be picky. ("I want a job in Italy only for no less than US$90,000.")
Couples and Dependents
The rule of thumb is one dependent per one full-time contract. (A non-teaching spouse is counted as a dependent.)
While many schools welcome teachers with children, some schools do not accept any number of dependents.
Teaching teams are encouraged to apply. Most jobs go to those who have no more than two dependents (kids or spouses.) Again, it's a big world so there are always exceptions.
–Is there anything for non-teaching spouses?
Counselors, librarians, coaches, substitute teachers, school nurses, audio-video media specialists, and secretaries are needed and hired throughout the year.
Generally, a non-teaching spouse is considered a dependent. The rule of thumb is one dependent per one full-time teaching contract. Kids are usually enrolled in the same school, and the tuition fees are waived.
–How long are overseas contracts?
A two-year commitment is the usual requirement to qualify for the usual benefits, such as free air passage, housing / baggage allowances, insurances, tuition for dependents and the like. Most of these contracts are renewable, with a bonus.
Language schools (EFL/ESL) offer shorter contracts, from 2-3 months to a year.
–Do I need to know a foreign language?
No, you do not. There are very few schools and positions that require knowledge of a foreign language.