I really want to join an athletics club?

I really want to join an athletics club but how should i ask my parents? my friend trains in cardiff, but i cant make those days but there is a closer one to me that trains when i am free. I recently came second in my year in my school in highjump and it was the first time i tried it. The girl who won holds a previous record and i jumped the same height as her, but she won as she had less misses. I am also a keen hurdler and the second or third fastest in my year in my school? i am also a member of the cross country team. i won the under 14 discus 'B' title and made the final of the under 15 shotput. I can also do longjump. I can sprint, but im not the fastest. i tend to do 100m in about 15.9 to 16.1 second which i really want to improve. I am out most nights but i really would love to join athletics. how do i convince my mum?