越黎越渣

A professor and his three students A, B, C (in descending order of age) are having lunch to be paid by B, supposingly to "celebrate" B finding a job. Somehow the conversation includes something like:

C: 我比B 教過的
B: 我都比A 教過的
Prof: 而家D 學生越黎越渣
A,B,C: ...