I want to join the British Army as an Infantry Soldier but i don't know how to tell my parents i want to?!?

I am 15, 2 months old and i have wanted to join the Army as an Infantry Soldier. I have massive experience as a Corporal at the Air Training Corps in Wokingham. I have seen the closest Careers place in Reading. Which i tried to get my mum and dad to spot it.. so i got my little brother to tell them 'Jadon wants to join the army' but they took no intrest in it. So i have left a few tabs out on my PC so for when they come to pick it up they'll see what i want to do. For the Infantry you dont need any qualifications (grades) or anything, so i am half way there (i have an average A in english and a B in ICT and i am qualified in weaponry at the ATC. I have got off road driving qualifications and first aid qualified. I am fit fo my age (49 kg) and i am dislexic (but i dont think that'l make a difference to my want to be career) Buttttt i have a weenie problem it is my parents they only wanted me to join ATC as a fun out of school hobbie, but i have got into it sooo much that i want to join the forces. My mum and dad are worried about me (well i dont know) but i think that they will not let me join as an infantry soldier :( i need help of sneeky ways to get them to the careers office?!