Why do you want to? Are you up to something? You don't mention your age. If my kids were still kids today, depending on their age, I would insist on seeing at least some of their messages, just to be sure they aren't in touch with the wrong king of people. Parents protect their kids, or should; it's annoying to the kids but it's just the way it is.
Why not just limit yourself to texting age appropriate stuff so you have nothing to hide? After all who pays the bill for the phone? Yeah, that's what I thought. One more thought, so you figure out a a way to block your parents from viewing your text, then what? You tell them that you just quit texting? That your the only child in the USA that doesn't text? Get real. Give your folks some credit.