The goal of a parent should be to have a child behave correctly even when the parent is not watching.

Parents need to have honest discussions about many things including sexting. If a parent thinks putting controls on a phone or app is the answer they are very mistaken. A cheap WalMart "burner phone" solves that problem for any teenager with a little disposable cash.

Putting a "clever person" in what seems like a box to control their behavior simply makes them more clever. In the end it reinforces bad behavior to get around rules.

Is sexting a "good thing"? It depends on the person sending AND the person receiving.

The worst thing a parent can do is pretend if they don't tell their kids about sex they will never notice. Humm ... This only works if they are totally devoid of hormones.