I am regularly lecturing DS2, newly in Y6 about how 'forgotten' this/that and the other won't be chased up by teachers next year. Once it's carelessly left around (in a 1450 pupil school), consider it gone, sunshine!
TBF I am trying, instead of listing what he must do or must take, asking him to stop and think about it himself, along the lines of 'OK DS2' (catchy, huh?!), 'what day is it today? What does that mean? Okay, yes, you will need that object. Are you sure that's all?' (even if it is!). Or I will say 'OK, you're leaving the house in 10 minutes. Do the things you must do before you walk out. You know what they are'.
I have found that this focuses the mind.
DH and I had got into a slightly daft habit, born of being ignored til the third repetition, where we'd say, literally 'Put your shoes on put your shoes on put your shoes on', and they'd say 'OKAY!' but as I pointed out to DH, it wasn't making them think about What Must Be Done Next. It's hard sometimes because though you will get the 'Make them suffer the consequences' argument, sometimes those can be draconian, or in the case of an under-dressed DC on a day out, miserable for all as once the Lesson about getting ready properly has been delivered, you still have several hours of having to gauge the falling temperature, a deeply unhappy DC and possible health consequences!
FWIW an erstwhile militarily organised friend of mine suddenly left the camping holiday clothes packing for her 2 DSs, 11 and 13, to them. The week was punctuated with her endlessly trooping into the nearest town to buy shorts (only brought ONE pair of fleece tracksuit trousers between them ), PJs (none at all) and a sun-hat; but this was after an unpleasant walk with one DS getting sun-burnt and the other nearly expiring in the heat. One was also in her T shirts by the end of the week! OK, a lesson may have been learned but boy, we all suffered!