DS 17 spending all weekends with girlfriend and schoolwork slipping

[PeacePilgrim]

DS 17 has suddenly a girlfriend, we haven't met her, spending most weekends at her family house, stopped doing any additional school work, has worked so hard for GCSEs and in year12 to achieve great grades/ planning on applying to good universities

I am panicking feeling hus grades won't stay high his options will completely change not sure what to do.

Thoughts?

He has a full year to pull things back and prove himself.
Maybe allocate time for homework and then he can go to girlfriends house. It's up to you to put the rules in place.