Like a typical Asian kid, my best subject was math when I was younger (so was art and p.e. but those aren't really subjects) and my grades were pretty good if I do say so myself. But I was always got below average grades in English. I absolutely at literature and writing. This was a problem for me for a while, up until I was fourteen and entered high school. 

That was the year I took an interest in music and it became a part of my every day life. I listened to it every single minute of the day; when I woke up, when I'm showering, on the subway, and even when I sleep. Afterwards I started dancing and that's when my English grades went down to C+'s and B-'s (I'm Asian so I went to after school so the other subjects weren't a problem). So, I began a new tactic to improve my writing that may not work for everyone.

writing lyrics.

Personally, since I never really studied music but only listened to it I just wrote "English versions" of Korean songs. This helps with writing under multiple restrictions as well as creativity, and not to mention expand your vocabulary so you don't repeat the same word five times in one verse. Of course this is only to be done during free time since it can be a distraction if you truly do enjoy it (...guilty. lol i swear i have ADHD or something I can never concentrate on something. and I'm rambling again). Also this kind of works as motivation for me to write, whether I want to write about love, friendship, or life. 

For example, when I wrote english lyrics for tablo's bad, f(x)'s beautiful stranger, and exo's what is love i was able to write my three part essay in my academy about what is love and the multiple sides of it in twenty minutes. Oh, and a few years ago I wrote lyrics to SNSD's Born To Be a Lady and wrote a draft of my part of a group project on the meaning of life during school at lunch. And exo's xoxo helped me finally start my one shot. 

This is just a suggestion, so if you think this won't help at all, then just ignore this post lol cus i suggested it to my friend once and it helped him too (even though he was cursing me out saying it was too hard in the beginning).