If I was ever asked to give a speech to incoming freshman at orientation, this is what it would be. (Not that I don't give it in parts throughout the school year.)
OWN Your Education. It belongs to you. And it is your responsibility to see that you get it. It is not your teacher's fault if you don't learn. Nor is it your parents' fault. Or your life circumstances. An education is an inalienable asset: once you have it, no one can ever take it away. But no one can do it for you. You must do it for yourself.
MONITOR Your Learning. Only you can know whether or not you understand the ideas you are required to master. Only you can know if you "get" it or not. Only you can determine when you need help. Your parent tries to make this determination from your grades; your teachers analyze your assessment data to try to identify what you don't know when you don't know it. But they are not the experts. You are. Only you really knows what you have learned and what you haven't. You must monitor your learning and identify what you need help with.
ASK For Help. Yes, ask for it. Your high school teacher has 150 or more students to keep track of. Your middle school teacher has about the same. There is no way a teacher can keep the individual needs of every student at the front of her mind. You must ask. Most teachers will respond with an amazing amount of time and individual attention. But you must ask. If you don't want to ask your teacher, ask another teacher. Surprise, surprise: your teachers are not competitive nor do they have ego needs when it comes to helping you. Most teachers will help another teacher's students. ASK. Or find other tutoring resources. There are lots of options, but it is on you to take the initiative. Go back to the first item: OWN your education. Take responsibility for it.
MANAGE Your Time. Yes, manage it. You are not six years old any longer with a belief in a fairy-tale world. Things don't magically happen. Deadlines are real. The only way work gets done is when you do it. Apply yourself and schedule time every single day to attend to homework, projects, and other assignments that have very real due dates. Do it early. Don't come home from school to eat cereal and watch television for three hours until dinner, then spend the time until 11 PM texting, instagramming, snapchatting, and whatever else with friends, and then turn your attention to the 3 hours of homework you have which is due tomorrow because you left it until the last day. Manage Your Time. Get ahead of the workload and every due date will become easy to meet.
TRACK Your Assignments. Use a planner, keep up on your internet grade portal, write them down. The pitiful excuse that your teacher never told you about a homework assignment is first not true, because your teachers mention them repetitively until they mumble them in their sleep, assignments are written on a board in the room, they are posted on line ...
STOP Your Excuses. We are back to Number One: OWN YOUR EDUCATION. It is your responsibility and only yours. Your years in school are not about getting grades or worse, getting high test scores. Your years in school are about gathering knowledge about the world so that you can understand how it works, the natural world and the world of human society, and make your way successfully through all the years of your life.
I would say Good Luck, but you don't need it. We, your teachers and parents, stand ready to support you. But we cannot do it for you. However, once you decide to do it for yourself, you will find you will achieve your greatest dreams because we stand with you and behind you.