Parental Controls
If a Kids lock doesn't impose enough of a digital nanny on your kids, you can take things a step further and limit the maximum ratings (using both the movie and TV scales, e.g. PG-13 or TV-14) that can be accessed anywhere on the HBO app.

If you have HBO NOW, click your name in the upper-right corner > choose Parental Controls > Choose the maximum allowed ratings. You'll have to enact/enter a four-digit PIN similar to the Kids lock.

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