“Over 220 schools and 40,000 youth participated in 2013 Healthy Kids Colorado Survey.” - http://www.chd.dphe.state.co.us/topics.aspx?q=Adolescent_Health_Data [”About” tab]
Works out to a ±1.4% standard error for that 2% drop.
40,000 independent data points? You think 40k students chose to answer the question?