A teacher I know was recently on the receiving end of negative commentary because she was teaching a book at a lexile level lower than the grade level of her students.
Let me contextualize a little here and say that she teaches at a high school where some students were assessed as reading proficiently at a 2nd or 3rd grade level, many read at a 4th- 7th grade level, and a small percentage read at an 8th grade level or above.
Tim Shanahan has argued compellingly that lexiles are an imperfect measurement, and there is little, if any, evidence base for a reading instruction model that requires students to be taught texts at some optimal reading level, matched to their abilities. He also argues, and I agree, that students can access challenging texts with support. The Common Core standards say that students should be able to read “complex literary and informational texts independently and proficiently.”
However, I worry that teachers will interpret the Common Core standards and other such imprecations to teach challenging texts as a mandate to assign difficult fiction and nonfiction just for the sake of its difficulty. Too often, that means teachers simply explain what happened in, say, a short story, without teaching students skills for accessing texts on their own.
I think we need to be clear about our reasons for assigning a particular text with a particular level of difficulty. Is the goal to promote fluency, help students gain self-confidence, and grow their enjoyment of reading? By all means, teach something at a lower lexile level. Is the goal to teach students how to access those “complex… texts independently”? Then make sure to provide them the scaffolding and support they need to begin to appropriate the required literacy skills.