How to activate an iphone without a sim card?

I found an iPhone 3gs in school the other day and it was locked with an unactivated simcard inside. I factory reset successfully today and it updated by itself as well. After asked basic questions like the language and location, but then it told me to put in a sim card. I have an android with a sim card but then att will charge me for data plans which i do not have and it will cost more in the bill. Any way i can activate it without a sim card? I don't plan on using it for calling or texting, just for apps and games

Added (1). I found it and it was on my way to school not inside the school. And if i do that, what makes you so sure the rightful owner would get it.

Did it not occur to you to turn in the phone to Lost and Found, instead of taking someone else's property?

I really don't want to help you since its not yours but the last sentence you write was true so here you go: Jailbrake the phone really easy, and it won't ask for sim and skip cydia and stuff if you don't want to use them

Did it nt occur to you to turn in the phone to Lost and Found, instead of taking someone else's property?