I have run my multi-grade classrooms for students who struggle with mild to moderate learning disabilities and/or Autism Spectrum disorder as a Tier III intervention-type program. For English Language Arts, I use research-based materials and instructional strategies with built-in progress monitoring for easy IEP goal tracking. I adapt and add to these materials as needed (especially through finding great TPT resources). Because many students spend core instruction in the self contained classroom, I integrate grade-level core materials into our instructional day, where we differentiate and make accommodations and modifications as necessary so that the students are getting full "access" to their curriculum.
For my students who have more involved needs, I build my classroom around the grade-level social studies and science themes. I fold in literature and informational texts at the student's ability levels (I write many of my own simple "picture books" to fill this need.). I develop many of my writing prompts as a response to the unit of study. I also develop "art" projects to coincide with the unit. These integrate as many fine and/or large motor skills and cognitive skills that my students may have challenges with (sorting, cutting, glueing, following directions, etc...).