Not necessarily. Especially if the school he is leaving chooses to contest the transfer. Here are some hoops I would suggest anyone in this situation jump through:
change your drivers license to have your updated address, sell the house you are leaving (if you rent it to someone else it raises questions with the KHSAA), don't sell the house on a land contract - use a mortgage company so that the title is legally transferred, change your voter registration, sleep in your new home every night, have all phone, cable, and utility bills put in your new name and sent to the new home address (not a P.O Box)
I'm sure there are more things than this that have kept kids from being eligible, but these are the ones I know of. The KHSAA is not predictable and is inconsistant. Even when you move, you take a chance on losing a year.