Mobile phones are not paralysis to youngster's minds because although there is a lot of bad and unproductive stuff out there, there are still some useful things that can be acessed on smartphones. Students can contact teachers, consult with eachother about homework and help eachother out. Another reason smartphones are not terribly bad is that you can acess information much quicker, like if you have a reasearch paper due that week. If others have the same topic, books at the library could already be checked out, but on the internet nothing can ever be on "hold". The smartphones can quickly get you the information, and a lot more of it then if you consulted a book.
For my second argument, I will talk about videochat. If you are good friends with someone overseas or have family far away, you can use videochat to contact them instead of having to potentially thousands of dollars for plane tickets. This can be used to frequently see your good friends and family. This is yet another productive feature of smartphones when they are in kid's hands.
Smartphones are useful tools to kids because it teaches them responsibility. Since they like their phone so much, they will be careful not to lose it and this will help them develop future skills for life such as orginization. Also, parents can use a cellphone as a motivator, letting kids have it after they do something good, such as taking out the trash, washing dishes, setting table,etc.
The phones can help kids learn valuabe character traits that can be used later in life, when they really matter, but a cellphone gives kids a chance to hone these traits in a safe enviroment.