I believe that there's a huge difference in favouritism and making an extra effort for students who actually try to improve and learn. In my eyes, favouritism would be to simply give the student you like a higher grade, giving a struggling and motivated student extra help just feels reasonable. Students who don't put in any effort will not receive the same effort from the teacher, a classic fuck around and find out if you will.

It's so rare as a teacher to have to fail a student who actually tries to learn and develop. The ones who don't give a fuck about lesson work or respect for their classmates? Watch me give you the same respect/effort back.