obviously it depends on your school/college but based upon what I've seen at the 3 schools I've been to, with underperforming students their main motivator for making students drop out is to try and maintain their results statistics. It would definetly be better for you to try and get some alevels. The only other option would be for you to start the year again, the teacher may just have been concerned that you have too little time. Even with no revision, failing exams still suggests that you have very little understanding of what you have coverered this year, and whilst you have 3 months you aren't really in the best position to do well in your exams.