最高學歷 Highest qualification

I like this funny experience of my high school buddy from HK,
it turns out really a good joke:
she works in an agent company to help people to get temporary visa to stay in HK,
she phoned one of the client who is now in mainland China,
and asked the client to send a copy of his highest education certification,
thinking he should have completed his Master education,
however,
at last,
she got a copy of his primary school certification,
she called him again,
and clarified with him,
the guy from mainland China said that,
yes,
he got the highest grade in his primary education,
thus he sent the primary certificate!