At my college the exam papers are already on the desks before we go into the exam but no teachers are allowed into the exam room before the students get let in then the only get to have a quick look through the paper after we have started the exam and if anyone is on clash timetable they have to stay in the exam room with the invigilators during the time between exams so they cannot get any hints from teachers or other students.
It depends on the school and the subject i think. My maths exam was in the afternoon so we spent all morning with our maths teachers and a few of the questions he gave us were almost identical to what was in the exam, just a few letters were changed, the numbers all stayed the same. He didn't actually tell us that was in the exam but we all knew anyway.
Something similar happened with my biology and chemistry but i think that was more of the teachers guessing what was in them rather than actually seeing the paper. I guess i just had really nice teachers
That's a tad unfair on the rest of the country's pupils I say. Seems too much of a coincidence for the questions to be the same as for the exam.
i was talking to somebody who is a courier, and he actually deals out the exam papers to the schools in the area where he does it. and he said that if any package contaning exams even remotely looked like it was tampered with he would get a £250,000 fine!!!!!!!!!!!!!!!!!!!! all in all not worth cheating,