I instructed recently for a new program organized by the Golden Gate Chapter of the BMW CCA. For those keeping notes, GGC was the club for whom I built the original prototype of MSR back in 2002.
GGC has a successful ladder system that moves participants from low-cost, low-commitment entry-level activities like car control clinics to higher-cost and higher-commitment events like autocross and HPDEs. The challenge they have faced is keeping advanced drivers in their program. Some go on to club racing, some become instructors, but others simply get lost in the vast wilderness that is "open track days".
If you're brainstorming solutions to this problem, you might throw out ideas like more track time, better instructors, or more liberal passing, to help retain those experienced students. Those might work but lots of groups do that. GGC tried something totally different. They purchased 7 GPS-based data acquisition units and invited 7 instructors with racing and data acquisition experience (who could translate the squiggly lines into meaningful instruction) to create a personalized "Advanced+" offering. An increased entry fee bought the use of the data system, one-on-one coaching and double the track time to apply and learn from the intensive instruction.