Immersive simulations are powerful teaching tools, particularly useful for subjects where a holistic understanding of a complex system is necessary. The authors have used several 6-hour table-top simulations to teach process improvement and engineering courses at Northeastern, George Washington, and Loyola Marymount universities. The pandemic forced a natural experiment. On-line versions of the simulations were created in commercially available software which recreated the experience of the in-person simulations directly, with almost all actions, lessons, discussion and planning sessions preserved. More than 120 students participated in the on-line simulations in 2020 and 2021. Before and after the pandemic (and during it, in hybrid classes), a large "control" group of students participated in the in-person simulations. Extensive data was collected including self-reported student learning, instructor evaluations of student performance and data from the simulations themselves. On-line simulations were assessed by students to be less effective overall by a small but statistically significant amount, but on most specific aspects of learning, and on student outcomes, there was no significant difference between them and the in-person versions. The existing difference depended on the degree of immersion in the simulation; fully immersive simulations were assessed to be fully as effective as in-person simulations. The virtual simulations were more work to facilitate. The overall experience is a proof-of-concept that virtual simulations can take the place of even complex inperson simulations with little loss of pedagogical effectiveness. The challenge is now to refine the simulations so that the need for faculty facilitation is reduced, and the level of immersion increased.