I recently experienced something like this in a club race, where 3 Leopard classes – Junior, Senior and Shifter were mixed in one run group.
I don’t think there is any problem with younger kids running w older drivers, as long as you can figure out how to equalize performance. And they should be racing as one class. But, I suspect the kids will be faster in many cases, raising objections from the adults!
On the other hand, within the senior class, I’ve seen very different driving and objectives from the younger group of seniors (say 17-25yr olds – out to prove something; very rough; lots of banging and pushing; no sense of mortality) versus the older seniors (out to have fun), which might put the pre-16 drivers (who don’t bang as much as the 17-25 year olds) in a dangerous spot.
At my previous club, we ended up splitting the seniors into 2 groups for this reason – a ‘Mediums’ for everyone, and a ‘Senior’ class for those of us that did not want the banging.
The issue I had with my most recent experience was that they had 3 classes mixed, with 3 different results tables, and the slower drivers were blocking faster racers from another class from passing, making for a dangerous situation, for example when the shifter missed a shift forcing my son to decide to either hit him or go off track (which he did), costing my son the win in his class.
Once people move into ‘cars’ or ‘open wheel’, the consequences of touching are much greater, and the intentional banging that exists in karting goes away – then you can mix young and old, as touching is not acceptable.