Agencies listed in this section are the official accreditation or inspection agencies that are run by the government, or have been given authority to accredit or inspect the schools in that country. These are not just membership organizations, but objective, arms-length and unavoidable for legitimate schools.
They are the most important tool a parent has for verifying even the most basic standards in a school, let alone excellence. Beware of the many lookalike agencies with fool-the-eye initials. Despite their assertions that this or that is "just as good", no agency is listed in this section unless we're as certain as we can be that it has real teeth and validity.
If the initials don't line up with those of one of the accreditation agencies listed in this section (and do ask what they stand for): red flag here. There are certainly bogus accrediting agencies, giving meaningless certification to equally bogus schools.
Some countries simply license schools, and others have organizations that are so influential that their league tables and rankings are confused with official status (like the Fraser Institute in Canada, whose Report Cards can make headmasters tremble across the land but which still don't make or break the legitimacy of a student's diploma. One more independent tool, yes, but not an official inspection agency.
Membership in some organizations (like the National Association of Independent Schools (NAIS)) or British Schools in the Middle East (BSME) is only possible if the school is accredited by an approved agency. Another membership organisation, the Council of British Independent Schools (COBIS), is so well respected that it is recognised by the UK Department for Education(DfE) and its members may join the UK teachers retirement and pension scheme. These are not official accrediting agencies, but membership in them does carry weight and serves as a marker for legitimacy.
There's no gold plated guarantee that all schools accredited or overseen by these agencies haven't lost the plot, but most of the time, it's a pretty good bet that you can depend on them as a base line for good standards. If you can't, this guide tries to tell you why, or what adjustments might make the difference.