How to generalize asking for highest level of education in international survey?

I'm currently putting together a screener to prepare for usability testing. This software will be used globally. I'd like to ask for the highest level of education and have the participants select from a list so that the analytics are cleaner than using an open text field.

The problem I foresee is that different levels of educational institutions do not map to each other across geographies.

The way I would as this question in the United States is:

What is the highest level of education you have completed?

• Some high school
• High school graduate
• Some college
• Trade/Technical/Vocational training
• Some postgraduate work
• Postgraduate degree

Is there a good way to generalize this question for a clearer, although inexact response?