Fewer than 13% of Colorado’s high schoolers last year reported using marijuana at least once in the previous 30 days. That is the lowest percentage since at least 2013 — the year before recreational pot shops opened in Colorado. The percentage of high schoolers who reported ever using marijuana — 26.3% — is 10 percentage points below 2013 levels. The numbers come from the latest edition of the Healthy Kids Colorado Survey, an every-other-year snapshot of the physical, mental and behavioral health of Colorado’s youth. The survey is a collaboration between the Colorado Department of Public Health and Environment and researchers at the Colorado School of Public Health.