British English help!

[pbnesbit at msn.com]

No: HPFGUIDX 12004

I've come across a term I don't quite understand in the UK edition, 
so maybe some nice person from 'across the pond' can help this 
American out.

In PS, Jo keeps talking about revisions in the terms of schoolwork.  
What is this?

Also, how long is summer vacation in a typical boarding school?  I 
get the impression for Hogwarts it's two months.  Is this normal?  

Thanks!

Peace & Plenty,

Parker