At BMW CCA events we require helmets the meet the most recent Snell ratings. Most instructors use and recommend a HANS device; they also use an intercom system like the type used by a lot of motorcyclists.The lack of helmets? It's a complicated issue with conflicting opinions. Here is one:
https://g80.bimmerpost.com/forums/s...97aa222126570f37c3867&p=31007928&postcount=17
The counter to this, the Ford Performance Racing School requires helmets and hans devices for their students. They discourage you from bringing your owne hemet because their helmets have the radios integrated.
I don't know if the policy has changed, but the last time I checked the BMW Nurburgring school did not use helmets at all.