Scratch

hey guys, im new to the site and i work for the boys and girls club. this summer i am going to be teaching my kids how to make games using scratch. im sure most of them will want to make a platform game. i have been making my own called elite crusher (halo based game). i have been teaching myself how to do things but i only have a week left till the kids get here and i start teaching them how to use this program. with my game so far i have got my sprite to move and jump. i have different backgrounds and a working splash screen. what i want to do with the game is to get the protaganist to jump on an eiltes head and have the elite dissapear and tie in a score for every eilte nutralized.different levels will come with different ways to " kill" the elites like plasma nades hitting the elites and killing them. i have been having problems getting the elite to dissapear when jumped on and that if i miss when i jump on its head and the elite touches the spartan then the spartan will loose health. PLZ HELP!