To help schools locate information on conducting their own criminal background checks for teachers, the FTA has collected the most commonly used tools in this article.

The first place to look are the National sex offender registries(free):

 US National Sex Offender Registry

 UK National Sex Offender Registry(no public listing available)

AU Sex Offender List(volunteer run)

CA(no public listing): Manitoba, Ontario

NZ Sex/Violent Offenders(volunteer run)

SA(no public listing)

 Keep in mind that these lists can be outdated and some offenders get off the list after a period of years. If nothing turns up on the lists, it's wise to conduct a criminal background check. This is not always easy and depends on the country, but for the US, it's as simple as sending your fingerprints to the FBI with $18 and a return address for the results. 

If a teacher has a clear criminal record from all countries they've lived in for 6months+, then it is sufficient to say that the school has fulfilled their responsibilities in screening their teachers. Additional screening would not be worthwhile unless there is a strong suspicion the teacher is a violent or sex offender. Under these circumstances, you can hire a private investigator who will check references, verify previous employment, check local/regional police and court records, as well as interview some people. There may also be investigators and police who can run a "sting" operation to catch a criminal.