I really can't even tell if you're serious.
If you're in the country then you visit the school and speak to the administration, staff and students. If you can actually meet, in person, a former employee, then all the better.
If you're outside of the country then you ask to speak to current teachers on the phone. Pick some names randomly from a list of teachers. They still might have an agenda but at least you can hear a voice.
In the end you're trusting yourself after you've made a more informed decision.