Oi! Yanks! No!

Education

Yeah, there is home schooling, but it's rare. BTW, we don't call the different years grades. They're called years.

Quick version

Nursery - preschool, 3-5 years old
Infants - Starts at 5, though some start at 4. Compulsory to be in school once 5.
Juniors - 7-11
Infants and Juniors are referred to as 'primary'.
Preparatory - 8-12, exclusively public or the higher class of private school.
Secondary/Senior - 11-16 or 11-18. Leaving age minimum is 16.
(Quick note : in public/private schools, the years in secondary from 11-14 are the juniors and 14-18 are the seniors.)
Sixth Form College - 16-18, post GCSEs.
Foundation - one year's worth of study, pre-higher studies, for more training/refining decisions. Normally vocational or art.
College - Refers to the more vocational higher learning centres, including art. Most of the old technical colleges have become universities. Anyone referring to a college at university will be at Cambridge or Oxford, where you belong to a college within the university. (correcting self - many of the larger unis have colleges within them, such as UCL)
University - Higher learning centre, post 18 for most people.

Definitions

Public - Selective, fee-paying school, normally the older institutions of great history and great snobbery. Often single-sex. Good examples are Eton, Rugby, Cheltenham Ladies' College and Harrow. You can tell whether someone went to public school by their accent. Part of the selectiveness also comes from birth and status. Normally boarding, though you will hear the term 'day boys'. ('public' comes from the fact that there used to be two types of school, church and public)

Private - Selective, fee-paying school, nowhere near as expensive as the public ones.

You can get into either of these via scholarship places, but these are rare. Small note :

Grammar - selective state school, on the basis of intelligence, parallel to secondary schools.

State - funded by the state or grants. Most people go to these.

Exams

English pupils are the most examined students on this earth, mostly due to the fact that the government introduced a whole load of tests throughout school life during the early nineties. We hates them, my precious. Don't even mention the words 'key-stage' if you want to escape with your life. Or AS.

GCSEs (General Certificate of Secondary Education) - taken at 16, wide range of subjects in practically everything. English and Maths compulsory. Most I've seen anyone take was 12, and they had no life.

A (Advanced) Levels - taken at 18, normally 3. Help determine which subject you're going to take at university.

AS levels - count as half an A-level, taken during the first year of A-levels. Don't even try to attempt doing this, as the system on these is in a state of flux and a complete mess. Mention and die.

GNVQs - General National Vocational Qualification = 5 or more GCSE's from C to A* depending on final grade (pass, merit, distinction)

AVCE - Advanced Vocational Certificate of Education. Advanced version of GNVQ (one year only course). can either be double award (2 years) or single (one) = either 2 or 1 A level, depending on award. Double award gets a double grade. i.e. AA, BC etc. first year grade + second year grade.

'O' levels - taken at 16 by the grammar school students when everyone used to be split into secondary modern and grammar pupils. CSEs (Certificate of Secondary Education) were taken by the secondary modern lot. This is pre-1980s.

University

Subject must be picked *before* you go, and compete and apply on the basis of that. You don't just go and then decide, you decide during your A-levels, then choose on the basis of that. Unis pick on the basis of predicted grades, written statements and interviews. Though once you've got in you can switch subjects and universities.
Normally a 3-4 year course, graduating with a bachelor's degree in your chosen subject (unless it's medicine or law). Most students have to pay fees to get in these days, means-tested. Nearly every student finishes with huge debts (the current average is Ł10,000), and most work during uni. Unless you're the kind of person where Daddy pays for everything.

Masters - one year course, not normally taken until older. Intensive and waffle-heavy.

PhD - you can get a doctorate without having taken a Masters.

Foundation - one year, designed to give you extra training and more focus. Like a prep course, mostly associated with art students, where it's the norm to do foundation before college/uni.

Stuff

Proms, Homecoming, etc, etc. - These do not exist, and we sit there in bemusement when they're mentioned. The most we have are the occasional school disco and the spring/may ball at the very end of school, which is just a dance in posh frocks where everybody gets drunk.

Nor do cheerleaders, pep rallies, sports people getting treated as gods, valedictorians, cliques and fraternities. Everyone just gets on with life.

Greek letters - only found inside greek class and maths. Like we said, fraternities no exist and we think they're weird.

There is no special graduation ceremony after school. You just leave. No certificate either. University, there is, where caps and gowns are indeed hired, but this is traditional.

Uniform - most schools wear this, except in 6th form (the last two years, 16-18). Shirt, tie, sweater, skirt or trousers in the school colours. Sometimes blazers too. The really stupid variations designed to make you look a twit are only worn by some public schools.

Faculty - never use this word as a collective term for teachers in normal school. They're the staff, not the faculty. Faculty is a term reserved for university teachers, where you have such things as the 'Faculty of Medicine'.

Form - either a class or the old term for a year.

Prefects and Head Girls/Boys - members of the Sixth form / Year 12 who organise and take on some of the duties of the teachers. Mostly to do with controlling the younger ones.

Upper one/lower two/upper fifth - old names of the years. Still used in some private and public schools. For simple purposes, U3 is the 11-12s, the fifth year are the 14-16 year olds, and the sixth are the A-level students. Most schools use the simple form of counting up from infants.
Another quirk of the public system - anyone below the fifth year is referred to as a junior, anyone of the fifth and above is a senior. No, I don't pretend to understand either. But it's much less confusing than 'sophomore'.