It's like code_colossale says: Exams are stupid and so are grades

You should study piano/music for the love of... piano music, getting a grade might give you a minor sense of achievement that lasts about 12 seconds... then what?
The fact that you worry about what your friends might think and that you considered lying to them is worrying, re-evaluate why you are doing this please.
"I have come to realise that it is better to play lots of pieces at a particular level than just two or three pieces for a 6 months to a year for an exam until you are so sick of them, you never want to see them again." - I want to comment on this one. You should not underestimate the value of STUDYING a piece for a considerable amout of time (not repeating it everyday without giving it much thought). There is a lot to learn from a single composition, some things you only discover after maybe 6 months or whatever timeframe. However, you will not be able to do this if you don't love the music. If this is a piece given to you by your teacher and you don't particularly like it, it is impossible to spend that amount of time and concentration on it.
You study in a school, schools use methods, methods are like exams.
If it is possible for you, look out for a good private teacher. You can tell them what you want to learn, they can guide you to achieve your goals (they might assign you pieces for this but you will have very specific goals in mind) and you will not have to worry again about studying a piece you don't really like, to play it for people you don't even know, who will then "grade" you on it.
I value the idea of an (in)formal recital much more. Just playing to music you like with no strings attached.
Good luck and enjoy playing