salam
well concerning stress ,it's no longer taught for the MS1 & MS2 levels for the M3 7 MS 4 level it's taught in very simple way and specially for the MS4 level it's not planned in the BEM exam.
If you need lessons about stress ( academic research) I may provide you a book of Peter Roach but if it is a matter of teaching in middle school you can have a look at my lesson plans for the MS3 you will find very simple Tips for the learners because teaching stress in detailed way is very hard for our learners so I advise you to follow the Tips of the MS3 level for MS4 I advise you to focus on the BEM typology .
good luck