If they can take a phone in instal an app that puts the phone in silent do not disturb mode for school hours plus a few extra minutes that way they don't have to remember to turn it off or on.
Make them more aware of their surroundings. Is anyone following them? Teach them that no adult asks a child to help them look for their lost dog or load something into a car. Teach them to say no and not people please. They can practise this with you and with a mirror so they can do a worried face and then a confident face. Also the puzzled face and a "yeah, whatever" comment to anyone who tries to belittle them. Learn breathing techniques for when they are worried.
If they need help go into a shop or ask a Mum with children with them. So basically making decisions about safer options.
If they are letting themselves into an empty house, key in the door, unlock, remove key open the door, shout hello, put it into the lock on the inside, lock the door and then turn off the house alarm.
Definitely check their messages and to not go along with nastiness toward another child. We called it being a Neville (Longbottom from Harry Potter, standing up to your friends is hard)
And lastly get them to solve problems at home, let them work things out rather than telling them what to do.