flunk out
phrasal verb with flunk verb [ T ] mainly US informal uk/flʌŋk/ us/flʌŋk/
US informal
（因学业不好而）退学
to have to leave school or college because your work is not good enough
Dan won't be in college next year - he flunked out. 丹明年不会继续上大学——他成绩不好退学了。
Compare: send someone down (COLLEGE)