Shoe sizing problem?!

Shoe sizing problem?

ok so i went to the mall with my mom..and it is about 2 months before school starts for me (9th grade) (im 14 years old) well In a K-Swiss shoe i ware a size 11, but in a Nike shoe I ware a size 9.5 and thats when my big toe is about 1cm from the end of the shoe...why is there such a difference between sizes in different brands..well anyway I bought the nike shoes in a size 9.5...and my toe is about 1 cm away form the end of the shoe..well these shoes are for the school year..so im saving them for 2 months..well when i got home my dad was mad at me cause he said my feet are going to grow by the time school starts and my shoes will be to small to ware and i spent $65.00 for nothing...do you think my feet will grow that much in 2 months...my feet are already big ( 10 1/2 inches) so will they grow that much before school starts...is my dad rite about this?? should i exchange them at the store for a 10 size (.5 bigger) ?

help

I suggest holding onto the receipt and not wearing them until the school year starts. Then if they are too small you can always return them, if not then you just saved yourself a lot of trouble.