I'm in Upper Sixth of a King Edwards school atm. I'm internal not external but I can say that the majority of external students fit in well as long as you try and make friends. There is an external society sort of thing at ours where they meet up and make friends with each other so I imagine that's good to break the ice. my school particularly has high standards when it comes to education. Using the metric that homeland.lsw used, around 20-25 of the students in our year of 130ish make it into oxbridge and probably a dozen more into medicine. Coming from that, you'd think that they make you work your socks off, but I'd say that the workload really isn't that bad. It changes from teacher to teacher. Some teachers like to give you like 4 hours of work in 1 go and tell you that you have a week or more to do it. Some give you small half hour worksheets every lesson. I think I prefer the 1st way to be honest. I just end up using my free periods to do little worksheets I've forgotten about while playing pool lol. I'm not sure how big the workload is for comp school etc. so I cant compare sorry, but hopefully an external who went to a grammar school can chip in.