Solvemoji is a website that has puzzles ready to be solved. The puzzles are arranged by difficulty and each one is represented with emojis. An example is seen below. At the bottom of the puzzle is a place to put the answer in to check.
Embedded below is a 1 minute and 27 second YouTube tutorial. Please note that your district may bock the site - just be sure to ask if it can be unblocked.