We've never read our daughters' texts. When they first got phones, we went through the bills with them, looking for calls and texts at times they should not have been making calls or texts, teaching them how to use them responsibly.
They're 15 and 19 now, but at no time did we wellfeel like we needed to invade their privacy in such a way. We've always had good, open relationships with them. Spying sounds like a good way to lose a lot of communication in a search for a few mere facts.
Perhaps it helps that I was one of their middle school teachers, so I knew all their other teachers. I knew all the teachers at their elementary school long before we had kids, and I was those those elementary teachers' kids' teacher. Same with high school. We were active in their school from the first day of K, so we know their friends. We know everyone our kids know, and they know everyone we know, at least we did until eldest daughter left for college.