Original sentence: And three subtjects are carried on from the previouse year into A2 year once again the exams are taken at the end of the year.Normaly the student selects four subjects to continue on from the GCSE's they have just taken for one "AS" year ,the AS exams are then taken at the the end of lower sixth.Sixth form is not compulsery in england and wales; however if you intend to go to a university  then you must normaly have 4 AS's (obttained in the lower sixth) and 3 A2's.The marks attained are added up into UCAS points the number of which you have will allow or deny your entry to your chosen university
Edited sentence: Sixth form is not compulsory in England and Wales, however university entrance normally requires 4 AS's (obtained in the lower sixth) and 3 A2's.Students usually select four subjects from the GCSE's they have just taken, for one "AS" year, the AS exams being taken at the end of lower sixth.The marks attained in both sets of exams are converted into UCAS points, which must meet the offer made by the student's chosen university.Three subjects are then carried into the A2 year and further exams are taken at the end of that year