http://www.europass.it/en/europass-study-visa.html

"If you are a citizen of a member country of the Schengen States or if you come from one of the countries listed below, you do not need to request a visa for study purposes for stays under 3 months’ length.

Schengen States: Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland, Slovakia, Slovenia

Other countries: Andorra, Argentina, Australia, Brazil, Brunei, Canada, Chile, Colombia, Costa Rica, Croatia, El Salvador, Guatemala, Honduras, Hong Kong, Israel, Japan, Macao, Malaysia, Mexico, Monaco, New Zealand, Nicaragua, Panama, Paraguay, Singapore, South Korea, USA, Uruguay, Venezuela"


http://www.learn4good.com/travel/es_visa.htm

"Student Visas for Spain:
This type of visa allows you to study or do research work in Spain for periods exceeding 3 months.

U.S. citizens do not need a visa to study in Spain for less than 90 days."

Google is your friend.