This is terribly difficult to judge without knowing your parents but the answer is simple. Just be the person they thought you were, not the person that they now suspect you of being.
Imagine how your parents see their model child and write out a list of those qualities that you wish to re-establish and find small ways to show them every day.
Obviously, you could also write them a small letter, expressing your deep sorrow at letting them down, expressing that it may be hard to trust you now, but that they are the most important people in your life and that you will build it again, no matter how slowly. Your willingness to do this will certainly score points. Don't spend much time talking about it with them, unless they ask, because you don't want to remind them of it.
Like I said at the beginning, be the person they thought you were.
Imagine how your parents see their model child and write out a list of those qualities that you wish to re-establish and find small ways to show them every day.
Obviously, you could also write them a small letter, expressing your deep sorrow at letting them down, expressing that it may be hard to trust you now, but that they are the most important people in your life and that you will build it again, no matter how slowly. Your willingness to do this will certainly score points. Don't spend much time talking about it with them, unless they ask, because you don't want to remind them of it.
Like I said at the beginning, be the person they thought you were.