Song writing is difficult at the best of times so I am going to give you some tips on it
1) Don't force yourself, only write when you have inspiration
2) Don't write about something you haven't experienced I.E Love, Depression
3) it doesn't always have to rhyme
4) Carry a scrap of paper/ notebook with you at all times just Incase a though hits you
5) Listen to other peoples music to give you ideas.
6) Decide what type of music suits your voice.
7) If you are bored in class then try to write a song, it always helps me.
8) Think of the lyrics FIRST