You may not want to show your grades to your parents but they may feel entitled to them anyway. And, surprisingly, your parents may have been told by the university that the college is unable to give out your grades to anyone but you. So what's the deal?
While a college student, you are protected by a law called the Family Educational Rights and Privacy Act (FERPA). Among other things, FERPA protects information that belongs to you -- like your grades, your disciplinary record, and your medical records when you visit the campus health center -- from other people, including your parents.
There are, of course, some exceptions to this rule. If you are under 18, your FERPA rights may be a little different than those of your over-18 peers. Additionally, you can sign a waiver that allows the school to talk to your parents (or someone else) about some of your privileged information since you granted the school permission to do so. Lastly, some schools will consider "waiving FERPA" if they feel there is an extenuating circumstance that warrants doing so. (For example, if you've engaged in a serious pattern of binge drinking and have landed yourself in the hospital, the university might consider waiving FERPA to notify your parents of the situation.)
So what does FERPA mean when it comes to your parents seeing your grades for college? In essence: FERPA prevents your parents from seeing your grades unless you grant the institution permission to do so. Even if your parents call and yell, even if they threaten not to pay your tuition next semester, even if they beg and plead ... the school will most likely not give out your grades to them via phone or email or even snail mail.
The relationship between you and your parents, of course, might be a little different than the one the federal government has set up for you through FERPA. Many parents feel that because they pay for your tuition (and/or living expenses and/or spending money and/or anything else), they have the right -- legal or otherwise -- to make sure that you are doing well and at least making solid academic progress (or at least not on academic probation). Other parents have certain expectations about, say, what your GPA should be or which classes you should be taking, and seeing a copy of your grades every semester or quarter helps verify that you are following their preferred course of study.
How you negotiate letting your parents see your grades is, of course, a very individual decision. Technically, through FERPA, you can keep that information to yourself. What doing so does to your relationship with your parents, however, can be a totally different story. Most students share their grades with their parents but each student, of course, must negotiate that choice for himself or herself. Keep in mind that, whatever your decision, your school will likely set up a system that supports your choice. After all, you are approaching independent adulthood, and with that increased responsibility comes increased power and decision-making.