I did bad on ap test?

Well it stands to reason that if you don't tell them, they'll assume you got a bad score, although the result of that is something that only you know. As much as it's not going to be easy, the right thing to do is to tell your parents. Scoring poorly on an AP exam is hardly the end of the world; compared to doing poorly on the SAT which can doom your college chances, AP exams play a minimal to nonexistent role in the college process except for maybe the top 20 or so colleges, and their impact is most felt when you're already enrolled in a school and registering for classes, so don't fret about it too much. Just tell your parents and hopefully they'll understand that AP exams aren't as easy as they think they are.

With the exception of top universities and many liberal arts college, if it's clear that you're a science-math person, then performing lower in the humanities is not necessarily a detriment, although you're not as competitive as a student who's solid in performance in all areas, and at many liberal arts colleges, such disparity is often detrimental since it's not in-line with their philosophy of education.

As we all know, every person is good at particular things. If you are really a math fiend and you enjoy doing math and you can doing it well, you should be proud. I think AP classes do give you a precious experience and challenge, if you have passed the course with a nice grade, you should be extremely proud of yourself already. Also, only about half of the candidates pass the USH exam annually, (and most candidates are indeed top students) you are not very bad indeed. Even you have failed the exam, the experience and knowledge that you acquire should be more abundant than those who only completed regular USH classes. My teacher also tells me that even if one gains a 2 in the exam, he/she has in fact learned much more than he would have in a regular class. Therefore, be proud and cheer up!

Be honest. More harm generally comes from lying. They'll want to know your scores, and then you won't be able to do much. Maybe cry a little bit, and they'll feel bad and not crack down on you so hard.