Rates of current and lifetime marijuana use among Colorado high school students has dropped since the state made marijuana legal in 2012, according to a press release distributed Thursday by the Colorado Department of Public Health and Environment.  According to preliminary data from the state’s biennial Healthy Kids Colorado Survey, in 2013 - the first full year the drug was legal for adults 21 and older - 20 percent of high school students admitted using pot in the preceding month and 37 percent…