They would have to get a special assignement but I have a family memeber that did the same thing; lived in Fleming Island and transfered schools to attend Clay High School. Let me know if I can help you in anyway.
I believe if the high school student lives in Fleming Island, then he/she goes to Fleming Island. At times, certain circumstances can change that ie. parent teaching at Clay, etc. , certain curriculum offered that is not offered at assigned school, etc.