Think of those coming next...
It may not be the case for all of you, but my position is being filled by another probationer next year. Even if this isn't what's happening to your role as the year comes to a close, have a thought for whoever is taking over your classes if you're not being kept on.
Remember what it was like the first time you took that fourth form, not knowing who was being quiet because they were shy, and who was quiet because they were secretly plotting how to blow up the lab and blame it on someone else? Who would hand in one A-grade assignment after another simply by being provided with the syllabus and a handful of notes, and who would need sat over constantly to get so much as their name on a piece of paper?
Think how much easier things could have been if someone had given you a register, a seating plan (so you could recognise faces straight away and ensure they were sat where they were meant to be) and a quick rundown of who/what to look out for.
Now, spend an hour or so doing just that for the person filling your shoes, boots, high heels, loafers, etc. With a bit of luck and some karma, this may come back to you in kind!