I started training four Chinese students a few months ago with an 83% pass rate (12 passes and 2 fails). These guys were a struggle to get through Private Pilot but, the first two passed and the last two failed; I am reluctant to sign the last two off gain. This gives me a 77% pass rate now (14 passes and 4 failures). I recall hearing something about dropping below an 80% pass rate and having two or more failures in a row. Has anyone had any issues with this? Will get the attention of the FSDO?