以下說話英文應該點講

I go to school every other Thursday. (make sure that Thursday is capitalized)

every other means 隔. (every other day 隔日; every other week 隔週; every other month 隔月)
Hope this help!

2006-12-03 11:29:17 補充：
樓上那位用的fortnightly有點怪怪的. 在美國, 我們都是用 every other xxx. I believe this is more suitable for general conversation.

I have to go to school every second Thursday!

I separate a week to just need to go to school on Thursday each time

I go to school on Thursday fortnightly.

fortnightly=兩週一次的

2006-12-03 11:23:26 補充：
fortnightly 解作(adj) 兩週一次的 (adv) 隔週地