Convincing guidance counsellor

I got the worst Bio teacher in the school bro she somehow manages to NEVER give 95+ in a STEM subject and all she does is get students to read out loud from the textbook every class. Class avg according to seniors last year was ~60

What is a solid excuse to change teachers??? I cannot say I just want a different teacher or they won’t accept it. My schedule is very flexible bc I have spares.

My spare that semester is first period and I have her second period. Idk if I can say something about the timing? Gosh pls help me she will tank my average