Do you think this is unfair?

I've already hated school but my hated just reached a new level.. So it's my final year of highschool- I got my marks and everything. The whole semester I had an 80 in English I finished 95% of my work on time and I ended up getting a 60 on my IRP which is shocking to say the least. I worked really hard on it but I thought my presentation would raise my mark up because I honestly thought I did awesome on it...well guess not. And then the final exam I thought I would AT LEAST get a 75 because in my mind it was well written, informative and well organized.. then I found out I got a 64 on it. I don't know why my teacher suddenly changed her attitude towards me. When at the beginning I was writing the exact same way and got 80's for my work. Now I finished the class with a 72. My friend who didn't do any of the work and the work she did do was around 6 weeks late finished the class with a 70. I got an 83 last year in English so I think this teacher is being biased towards me... Is it smart to contact the principal?