Depends on your interests? I've heard (friend of a friend - several friends actually) that Fort St is better at Music and Art and so on. Their school band is supposedly way better than Sefton's (once again, a friend of a friend).
Oh, Sefton's uniform is BLUE (or, blue and white), whereas Fort St's is red/maroon. C'mon, go BLUE.
Sefton's also half-selective, and in senior years, the classes become mixed, it's not a bad thing.
THe old principal used to give Sefton shuffle days and mufti days- not the new one though.
No offense @ c0okies.. but I wouldn't look too much on the academic level. What koombaya says does have some reliability and substance. The academic level mostly depends on the individual and your own motivation ot do well.