Can I drop to 4th year?

Last year when I was in 3rd year I made a foolish decision to take my 4th year application form out of the school because I didn't want To do it at the time.before I took out my application form I had asked a teacher if I wasn't able for the leaving cert would it be possible to drop down to 4th year and he/she said something could be arranged because of my young age, and now that I am in 5th year I'm finding it very difficult to keep up and settle in, this is making me extremely uncomfortable and unhappy as I am getting very stressed. I know I am not ready or mature enough for the leaving cert at this young age. I said it to the school numerous of times and my parents have been up to the school having meetings trying to arrange something and the school told them there is no room even though it is the smallest 4th year group the school has had and last year there was over 60 girls in 4th year and they let a girl drop and this year there is only 43 in transition year, I think it's just an excuse they are using. There was a letter wrote to the board of education about it an they can't do anything to help me.i think every student should be able to drop down to 4th year if they aren't ready for 5th year. Do I not have a right do drop as I am not copping very well and am so unhappy?