I am doing the same as you (except I'm working with K-2 writing teacher). We discussed splitting the class to teach the same topic in whole group, but with smaller groups. We also discussed her teaching one concept while I teach another concept. We also discussed her teaching the topics, and I would create activities for the students. We also have 30 minutes of whole group, 30 minutes of stations, and 30 minutes of intervention time. I help in whole group with guided practice, assist in stations where needed, and pull my group for 30 minutes of intervention. Hope this helps!