By the time kids get to high school they either already have the order of operations mastered or no amount of remediation can help.
This two day lesson takes a different approach by setting up clever problems for the students where they change what's written by adding parentheses to group things, changing the order of calculation to arrive at a pre-determined answer.
What happens is misconceptions are exposed, which then, in turn, allows students to replace their misunderstandings with correct understanding.
The first day's lesson gives students things like 3 x 2 + 5 = 21 and they have to place the parentheses appropriately to make it equal 21. It is a powerful learning experience for the students, but you must facilitate a lot of group work and discussion.
The second day's lesson is closely modeled by this video: https://youtu.be/-P884DAepn0 It really should address how all of the operations can be related back to addition, which is basically just counting. It's a powerful realization for students to experience.
There is homework for both days that really will make the students think about numbers.