I can tell you I probably didn't have the attention span to have passed the PPL exams at the age of 15. Just wait until you get to the Navigation exam & aeroplane technical.
Get lots of practice papers from your school and if available the PPL confuser. Answer questions by going into the book and finding the answer.
Read the book more than once. Draw pictures and diagrams of stuff (ie various lights and signals). - If you put real work in you WILL pass.
Also ask your instructor for briefings on things you dont quite understand.