How to let Xcode build apps and use playgrounds when parental control is enabled
From my testing, I have found that if the "Limit Applications" check box in Parental Controls is turned off, but Xcode and the other applications that you want enabled are turned on in the "Allowed Apps" list, Xcode will only ask for authentication a few times:


On the first run of Xcode
On the first attempt at running an app created with Xcode
On the first attempt at running a playground


Even though it sounds weird to turn off Limit Applications, it seems like if the parental controls are set this way, Xcode will not repeatedly ask for authentication.