Student teaching

I am currently a student teacher in kindergarten. My teacher associate told me that this is the worst group she had in her whole career and if it wasn’t from me, she would have gone on medical leave due to the impact on her mental health. To be honest, if this was my first teaching placement, I think I would’ve quit this field. I could write a whole novel on the difficulties of this placement. I am feeling so tired and overwhelmed from this, but I am not gonna go there. I am told I am doing almost everything right and it’s really just this group… So basically, my question is this: do you think it’s fair that the teacher decided to keep a student teacher even though she knows this is the worst group she has ever had ? She has 15-20 years of experience and she wanted to quit. What about me? This is my first experience with this age range. Knowing that she could have stepped back and I would have been placed with another teacher/group. And where I come from, teachers who take student teachers receive a nice bonus. I feel like I’m learning nothing and just in a constant fight or flight mode.