Should I use the verb "class" or "classify"?
Class is a noun that has been used as a verb since around 1642 (see Peter Shor's excellent comment below). However, Classified is preferable in this instance, especially when written. http://www.merriam-webster.com/dictionary/class
A seasonal example of the annoying trend of making verbs out of random nouns is "gifting." http://www.merriam-webster.com/dictionary/gifting