I know of a lot of people who have done there A levels from Beacon House in Lahre. Another one is Aitchison College..I don’t remember if they have A levels or Higher Senior Cambridge..I will find out.
If the student is a girl then Lahore Grammer is a good option too.
Beacon House is a Coed school while Aitchison is All Boys and then Lahore Gramer School is all girls.
here are some Links
Aitchison College
‘A’ Level Admissions - Aitchison College, Lahore](http://www.aitchison.edu.pk/index.pl/a_level)
Lahore Grammer School
Lahore Grammar School :: 55-Main Gulberg ::
Beacon House School
Beaconhouse School System