I think you'll find drug use at all of the schools. Bullying happens everywhere too, it's largely about how the school handles it.
I've only heard positive things about APS but the catchment is now so small, it's really hard to get in. Otherwise, I'm really not impressed with the other schools.
I know kids and parents who are happy with Fortismere but it struck me as completely chaotic and pretty run down when we went to the Open Evenings. I've also heard horror stories about bullying, fights, smoking, drugs, etc.
HWS is very similar to Fortismere these days. DC is doing well there academically but pastoral care is not the best. There are some really good teachers but also quite a few disappointing ones.
If your child has any SEN or other needs, I wouldn't send them to either school.
I've heard that Heartlands is up and coming,but I've never seen it and I don't know anyone with a child there.
A lot depends on the individual kid. Some really thrive in these big schools and Fortismere does have better extracurricular options than HWS. Other kids do better in smaller schools; but, unfortunately, there aren't really any good options for those kids. There are some smaller schools in Barnet but other than Friern Barnet School, the catchments won't reach into MH.