How to label a kid's backpack and gym bag so it comes home
Any school office will tell you the same thing: lost property is mostly full of good, expensive items that nobody can return because nothing on them says who they belong to. A bag that is labelled well comes back within days. A bag that is not gets donated at the end of term.
Label the bag, not just the contents
Most parents label the water bottle, the lunchbox and the PE kit, and leave the bag itself unmarked - which is backwards, because the bag is the thing that gets left on a bus.
Labels also need to survive. A name written in marker on nylon fades in a term of washing and rain. Sewn-in tapes work but are invisible unless someone is already looking inside. A tag that hangs on the outside is the one that gets noticed by the person who picks the bag up.
What to put on it, and what to leave off
This is where the balance sits. You want enough for a stranger to contact you, and not enough for a stranger to identify or approach your child.
Include: the child's first name only, and a parent's mobile number. That is genuinely all that is required for a return.
Leave off: your surname, your home address, the school's name, and your child's full name. A tag showing a full name and a school gives anyone the ability to greet a child by name and sound as though they belong there, which is the exact thing you are trying to avoid. The same reasoning applies to adult luggage and is set out in what to write on a luggage tag.
A covered card slot is worth choosing over an open window for precisely this reason - the details are there when someone looks, rather than on display to everyone in the corridor.
Make it visible in a pile
Twenty navy backpacks on the same hook rail look identical to a nine-year-old in a hurry. A tag in a strong colour, hanging from the top handle where it swings, is the fastest way for a child to find their own bag - and children are considerably better at recognising a colour than at reading a name label on the underside.
Colour also helps you at pickup, at the pool, and at the airport, which is the same principle described in spotting your suitcase at baggage claim.
Choose something that survives a school year
A school bag gets dragged, sat on, rained on and thrown into a corner roughly two hundred times a year. Elastic loops perish, plastic windows crack, and paper inserts turn to pulp.
A full grain leather tag such as the Riva Address Tag handles that treatment easily and can move to the next bag when the current one wears out, which for a growing child is usually sooner than the tag itself would fail.
A note on trackers and children
Bluetooth trackers in a school bag are increasingly common and can genuinely help with a bag left on a bus. Two things to be aware of. First, they locate the bag rather than the child, and it is worth being clear with yourself about which one you are trying to solve. Second, modern phones actively alert people when an unknown tracker travels with them, which is a deliberate anti-stalking feature and can cause confusion at a friend's house. How those alerts work is covered in tracker anti-stalking alerts.
The five-minute version
One durable, brightly coloured tag on the outside of the bag. First name and one mobile number on a covered card. No surname, no address, no school. Repeat for the gym bag and the instrument case, and lost property stops being your problem.