It is true that I'm the youngest and the least experienced worker in the company (19), therefore my boss always leaves the more challenging tasks for my colleagues. Although my colleagues envy me for working less and getting the same salary they're getting, i think that the boss is still skeptical about my skills and ability to work on challenging tasks. while learning how my colleagues do things I have to show the boss what i'm capable of otherwise my name wouldn't be on the list when there's a vacancy at a higher position. Basically i have the skills required, just not experienced enough, What are your suggestions?
Tell him that you would like to lead on the next challenging task and be judged on the results. Assuming it all goes well at that point you should be in line for a promotion and/or a salary increase.