I challenge anyone to accurately count a school of fish over 10... I have 20 Rummies in a tank and know that only because I haven't seen bodies. Counting them? No way! lol
i don't think it really matters and even if u are using a ratio of 1m:2f you can still have odd or even number schools. ex. 10 males 20 females is a school of 30 (even) 11 males 22 females is a school of 33 (odd)