I use this in-class exercise after I have taught the students how to construct LGOs using the generator orbital technique. The previous week, they do an in-class exercise on that topic, and this week, they use the LGOs from the previous week to construct MO diagrams.
Given a centrosymmetric molecule, a student should be able to construct its simplified, σ-only MO diagram.
The students work in groups of 2 to 3. Sometimes I match up "weak" and "strong" students and sometimes I let them pick. I haven't really noticed much difference. I circulate and give the students hints, and each group puts its MO diagram up at the chalkboard. If there is time, I have each group go through the construction of the MO diagram, but often I just hit the highlights.
I have homework assignments on this exact topic the week after they do this exercise. I also make sure they know that this WILL be on the midterm and final exam, and I don't disappoint.
All students have a complete (and correct) qualitative σ-only MO diagram for their group's molecule by the end of the class period. I collect each group's MO diagrams and post either the student-generated answer key or my answer key (linked to this LO) after class.
Some students do really well with this technique, and by the end of my course, I would say that almost all students are able to construct an MO diagram, especially if they are given central atom AOs with symmetry labels, and similarly labeled LGOs.