Cashboard (http://cashboardapp.com) is also a fantastic invoicing tool, and their free plan gives you some different options from what Freshbooks gives you.
Oh, news on this actually. They just posted this on their blog about a half hour ago:
Educational Licenses
We have had many inquiries for educational licenses. We are extremely excited that students are being drawn to RubyMotion.
"If you sent us a request for an educational license, please accept our apologies for the late response. We will start contacting you early next week. Your emails have not been lost!"