I know the school systems are very different between the states and England....I know that in certain circumstances, semesters can be totally wiped from your record. I had a friend do this, however, it was in college. My friend had a death in the family that sent him into a deep depression. He ended up missing a lot of school and got incompletes for Fs in every class. His dad wrote a letter stating what the death in the family did to his son (my friend) and the registrar dropped the semester from his record so that it wouldn't effect his GPA. He had to take the classes over again but it didn't effect his grades.

Also, something you need to remember is that, when colleges are looking at your transcripts and they see a semester or year that is totally out of the ordinary they will give you the benefit of the doubt. Like if you are an A, B student and all of the sudden you have a ton of tardies or absences and Ds across the board, and then the next year your grades are back up and your attendance is better it's obvious that there was something during that year that affected you a lot and made school very difficult.

Worst case scenario you could be put on a waiting list or something and maybe you could speak directly with the dean? There are always ways to get back on track and there are always people who want to help you and see you turn your life around. Don't get too discouraged!