What is your opinion about this ?

okay so i started going to a new school iv'e been there for a year now and after this week we will be moving up a year the problem is cause its a private school you have to be very smart and in my old school it was so bad and we didn't learn anything so i had to do a test to get into the private school im in now but i didn't do well but the headteacher liked me and saw something in me so she said that she was going to let me in however she put me down a year i was meant to be in yr 8 not in yr7 so later on in the year i asked her if i could go up a year and she said well its difficult but maybe and the thing is all the yr 8s are going to yr 9 which is the senior school another school and i want to go with them because i will miss them all.the thing is im not very good academically but personalty wise i should go up a year that's what the headteacher said so and i told her that my whole summer holiday i will revise but i have to revise a whole yrs work.so the question is should i go up a yr or should i just stay the yr i am in if i go up a year im happy but if i stay down i do better in school but im not going to be happy emotionally