Routines are HARD! They make you change your habits and getting into them can be challenging. But... they work.
You probably have a routine in the morning - and it works for you because you get yourself out the door without stress or frustration. Think about how routines for something like music lessons might relate. If a student knows they have to just do the thing, they do the thing! If it happens enough at the same time, with the same expectations, struggling to get students to practice starts to ease. So here is a routine that might help.
Straight from school, put the backpack where it goes, put the lunch bag where it goes, have a quick snack and then immediately to the piano. At the piano start with a scale or a finger warm up. Then do the first job on the practice page, check it off. Do the second job on the practice page, check it off. etc and finish with a piece that makes the student feel good.
Or: straight after dinner go to the piano, and warm up with scales or finger warm ups. Follow instructions on the practice page and end with either theory or a piece that has been mastered.
I know that I feel better when I know what to expect and routines can have this effect. Sometimes the practice is not good, but with a consistent routine those practices end up being productive in the end.
Have you tried a routine and has it worked for you?