Kids and school

I don't know what to do with 2 of my step-sons. They are failing school. They won't hand in work, won't bring work home to be helped with, and lie about having homework. One is in 5th grade and the other in 10th grade. I am so worried they are going to fail. I push them so they can graduate and go on to do the things they want to do. The 10th grader has already said he wants to go into the military and to college. I really want to see that happen, but at this point, I'm not sure where things are going. It is really rough trying to raise 3 stepsons with ADHD. Plus I also have a 12 yr old son. Four boys are a lot to handle when I am used to just one who gets the good grades and is a very bright, caring, and thoughtful kid. I don't know how to handle things from here. I have been married to my husband for a little over a year. Things can get very overwhelming at times, but we deal with the situations and move on. I just don't want things to get out of hand. M