Since there are so many ways kids can text these days, just being able to see text messages is not enough. There are many text messaging type apps that will be hidden unless you have the phone.
There are ways to set up to see SMS text messages, see Verizon Messages - Verizon Wireless, but understand your child is smart and will find other ways to text that you cannot track as soon as he or she figures out you are monitoring. The only sure way is as MiiHere states, and that is to look at the phone and have a rule you have the unlock code.
You can by taking the phone from them and reading the texts. If they were using something like Verizon Messages app and you had their log in info, you could possibly read their texts online or in their My Verizon.
What I would do is set up their phone for them and block all downloads. That way they are only able to use Message+ and then stipulate that if they want to have the phone they are not to mess with the text messages and at every random time I want their phone, they better produce it. Otherwise off it goes.