Do not sign off on a cross country unless you’ve verified they know what they’re doing.
Discuss this with the student.
Sit down and find out what the student thinks needs to be done.
Then tell them what you think needs to be done.
Show them requirements and regulations that make your point.
There will have to be some verification as to what they know and don’t know and can and can’t do.
Anytime this individual is flying solo it’s essentially on YOUR certificate.
You can’t defend yourself to the FAA by blaming the student and saying that you assumed they were proficient.
Is this at the same school or did he come from a different school?
Same school review training records.
Different school it may be worth to lay them a visit.
You may or may not have inherited a monster.