Steve Vandervelt, 16, an Arvada High School honors student, expressed grave concern Tuesday for friend Todd Wolk, who experimented with marijuana at a party the previous weekend. 'They say pot's a 'gateway drug,'' Vandervelt told Wolk. 'And even if it doesn't lead to cocaine and more serious stuff, doing pot can still really mess up your brain.' Vandervelt offered to speak to Mrs. Logan, the school's health-ed teacher, on Wolk's behalf to get more information about the dangers of marijuana use. 