When possible, their phones were even set to child mode, automatically blocking them from using their phones at their specific bedtimes so they can be really goody two shoes and not mess up the data.
And that bedtime routine doesn't have to be anything complicated, but it should be the same few steps done in the same order at the same time every night.
Make sure your bedroom is dark, cool, and peacefully decorated; avoid screentime right before bed; and try to maintain a regular bedtime to train your brain and your body to get primed for rest.