ACT Score in-depth analysis question about writing

I received a 35 on the ACT as an overall composite score which I know is a high score.
My math (my weakest, unfortunately) was a 33.
My English and Reading were both 35’s, and Science received a 36, which was rather surprising to me, since I thought I did terribly on it.
However, a couple weeks ago, I got my writing score back and was horrified to see a 31. I looked at the individual category scores within writing:
Ideas And Analysis 11

Development And Support 11
Organization 11
Language Use And Conventions 11
I heard the essay was graded out of 12, but it appears to be out of 12 for each category? Does this mean then that all 11’s is good, since it’s nearly 12, or is it bad, since the overall score appears to be a 31 out of 36? Can someone tell me if perfect 36’s and close to 36’s are rare? Thanks~

Ah - to make this post fit into the admissions category - how is a 35 with a 31 in writing for the Ivies? UC’s? Duke? Thanks