I am assuming that you are in college, because your parents would already know all of this if you were in high school. In any case, you sound like a big boy, and you need to face something here. If you mentioned only one time where you were trying to shift blame for what happend here to someone else, maybe an adult would buy it, but not twice in one question. The teacher is just not at fault for your grades, and the school is not at fault because they did not tell you something, those are big excuses that you are used to try and deflect some of this responsiblity.
Don't go there. Have some respect for yourself, and for your parents intelliegence, because they are going to see straight throught this tap and dance. Don't blame anyone else for your predicament, ever, and you have nothing to explain other than you are a human being and you made a mistake and you need to fix it. Pure and simple and all grown up.
What you are really asking, is how do I keep my parents from being disapointed in me, and how can I deflect blame? You can't. They will be disapointed, but they will be far more disapointed in you if you try to make it somebody elses fault. It is your fault, your class, your failure to contact that teacher and make the connection you needed to, yours. Every teacher is not going to be a perfect match for you, and if you are old enough to take chemistry, so you are old enough to know that learning the matieral is your responsiblity, and you have to learn it the way the teacher expects; getting it done thier way is also your responsiblity. You are responsible for going to the school to get a copy of your grades if it did not come, and it is your responsiblity to know the academic policies of the school you attend.
What you have to make them understand is that you failed at something. It happens, you either pick up the pieces and stop looking for someone else to blame, or you continue to fail, because you just can't do both and be a success.
Tell them, don't blame, tell them you failed and take responsiblity for what you have done and not done. If I am reading you right, it will be a nice change for you to take responsiblity and be a grown up and move forward and your parents will see a difference in you, uless you try to blame everybody else, in which case, be prepared for disapointment in both your grade, and your charachter. They will appreciate that you are a grown up, even if you have to do credit recovery or retake a course to continue your education.
M.