If you go onto the sprint website, under FAQ. You will see the question, Can I monitor my child's text messaging? Then you will see the answer, No, this feature is not available at this time. Hope that answers your question.
I see some people that make comments that parents should respect their children's privacy. As a child you should not have an expectation of privacy. Parents are trying to ensure the safety of their children. This may be hard to believe or swallow, but children DO NOT have all the answers and are not mature enough to make the tough decisions.
Here IS the answer to your question. Without an outside program Sprint phones or service will NOT provide an option to Monitor Text Messages. You must use an outside program like mobile-spy.com or others which only work on specific phones. These services have their own cost structure (about $100/yr) and provide you with an online interface to review all texts in/out as well as GPS tracking and other features. I've not used their service but I am shopping for a service to monitor my daughters texts. Good luck!