Writing and more writing

So, I'm in the middle of my student teaching for my ESL license. I was hoping to do more of my teaching in Spanish, but as I've chosen to teach about African folktales for Social Studies, and all the folktales I can get my hands on are in English, I'm having to teach in English. And, even though I seem to be code-switching very naturally, I've noticed that my cooperating teacher sticks to just one language at a time. When I asked her if this was deliberate, she said it was, which means I have to stop myself from randomly speaking in Spanish during teaching.
And so, I have been doing a lot of writing in Spanish instead. I have written a lot of essays, and various communications home that I have asked just about every Spanish-speaking adult in school to correct for me. No one has the time to sit down with me and discuss what I write, but I do get to see comments and corrections. I do feel like my writing has improved since the beginning of January, when I first took the Written Proficiency Test through ACTFL. I am trying to focus on writing in Spanish like I do in English - not limiting myself to writing what I know I can write correctly, because then, my writing sounds like that of a 5th grader. I know I need to repeat less, construct more complex sentences, and use better conjunctions and connecting phrases to make my writing sound more sophisticated. And one of the things that I'm finding is that I need to learn what those phrases, or ways of saying things, are in Spanish. After I learn what they are, I just need to memorize them. For example, in English, we say "That's Greek to me." In Spanish, the saying is "That's Chinese to me." There are many ways of phrasing things in English that are not possible, or simply not done in Spanish. I need the replacement phrases to make my writing more authentic, less choppy. And that's something that is going to come slowly...