What counts as a year towards the American Opportunity Credit?

My Son graduated from high school in May 2016.  The previous summer (June 2015) he took a college course online as part of a dual enrollment program where he got credit towards in high school diploma.  The college that sponsored his online class sent me a 1098T for cost of the online course and I entered it into TurboTax for my 2015 tax return.  This year he is a full time freshman college student at a different university.  Did I burn a year of the American Opportunity Credit when I claimed his online class in 2015?