Grammar, Usage / sentence structure question [13]

Sentence Structure Help

Hey I'm new to this site.
I have just finished my first year of a three year course here in New Zealand, my marks have been what i pesonally find acceptable, but the last few essays i got marks which i found to be not good enough for me, although a pass yay!

I have gone over years essays and the main comment which seems to be frequently written is about sentence structure. I was wondering if anyone knew of any either online or hard copy resources which might be able to assist me in improving my acedemic writing style and sentence structure.

Hope that someone out there can assist.

Kat