NEW YORK (AP) — Use of electronic cigarettes by high school students tripled over three years, according to a new government report released Thursday.In a large national survey last year, 4.5 percent of high school students said they had used e-cigarettes in the previous month. That’s up from 1.5 percent in 2011 and 2.8 percent in 2012.It’s not known, though, how many were repeatedly using e-cigarettes and how many only tried it once during that month and didn’t do it again.E-cigarettes began to appear in the United States in late 2006, but marketing has exploded in recent years. The devices heat liquid nicotine into a vapor.