One of the really big changes is going to be the academic pressures and expectations that are placed on you. While in the prior school years, there was probably a bit of leniency given in areas such as due dates for homework, project completion, and even testing methods in some cases, the expectations in high school are usually far more stringent. The teachers here will expect that you are responsible enough to stay on top of assignments, with or without the help of mom and dad. The old "dog ate your homework" type of excuses are no longer acceptable and there will be negative repercussions if you try to use them. They won't work and your grades will reflect that.
One of the troubles that students with ADHD have that impact their academic life greatly is that they tend to be rather disorganized and forgetful. In high school, you are going to need to come up with strategies that will help you to "get it together", so to speak, and keep yourself on track. If you have parents that can assist you with this, consider yourself fortunate, but if not, you must remember that it is your future that is going to be affected by the choices that you make during these years, so begin to take responsibility for yourself and find ways to succeed in the academic portion of high school by getting organized and staying that way.
A couple of suggestions for the high school student with ADHD to stay on top of their school and homework assignments are to get an organizer of some sort that you will use and maintain a good line of communication with your teachers. You may opt for an electronic organizer or one that is a paper and pen version, but make sure that you keep it with you and make a habit of using it regularly. Write down homework assignments, upcoming tests, and other things that you are going to need to remember. Look at your organizer daily, so that you can stay caught up in your work. Talk with your teachers, letting them know that you struggle with ADHD, but want to succeed in your classes. This will tell them that you aren't looking for an excuse, but that you aware of your weaknesses and they will probably give you some extra assistance in remembering what you need to do. Maybe they could send you a weekly email of your