A lot has already been covered in this thread so let's talk about the path to wheel to wheel racing. If you've ever thought or dreamed about it (and I know you have), what does that path look like...
A racing school is typically a 2 or 3-day course that is approved by a racing sanctioning body (like SCCA, BMW, POC, PCA, NASA, etc) that qualifies you for a racing license (also known as a amateur or club racing license). But it takes more than attending a race school to get a racing license.
(With that being said, there is nothing wrong with attending a racing school even if you don't have the experience to actually get a racing license. Racing schools are fun and challenging and you'll have a great time getting a taste of what it might be like racing even if you never get to that level.)
From the top level, the typical path to wheel to wheel racing is HPDE's, Advanced DE's/Time Trials, racing school, provisional racing, race license, and then racing. How quickly a person can move down this path varies with skill, dedication, time availability, and funding.
HPDE track days are great to get seat time, instruction, and learn how drive well. Basic car control and high speed driving technique is typically learned at this level. HPDE's are great fun in a Boxster and if you've never done a track event, you should. If nothing else, here is your chance to drive as fast as you like without your wife telling you to slow down.
Advanced DE/Time Trials come next. At this level, the goal is to refine your driving skills to a level where you can be safe in a race situation if you were to decide to go wheel to wheel racing. Qualifying for races is a lot like Time Trialling so if you can time trial well, you should be able to qualify well if you go racing. The main point here is that you should be a fully competent track driver at this level.
Next is getting into wheel to wheel racing and you'll need a racing license to do so. Most racing org's like SCCA, NASA, PCA, POC, BMW, all have a racing schools to teach the basics of race passing, driving side by side, driving off of the racing line, race starts, and other race specific skills. Barber and other schools are typically SCCA compliant.
But if all you've done is a handful of HPDE's and a 3-day Skip Barber/SCCA race school, most race org's probably won't let you out in the race group because you probably don't have enough experience or skills to race safely (drive side by side, drive off line, pass, etc). They will likely ask you to demonstrate your skills in Adv DE and if you do well there, then move you up to the race group to demonstrate your skills at that level and if you do well, then you're all set.
The point is that race org's have both licensing AND skill level requirements in order to race. Someone can't just go to a 3-day school and then go out and race without any other experience or without demonstrating competence at that level.
Once you're licensed, then you have to apply to each race sanctioning body (SCCA, BMW, PCA, POC, NASA) in order to race with them. The good news is that most of the other club or amateur racing org's will accept your license from another org (or accept it on a provisional basis that lets you race with them while you demonstrate that you know what you're doing).
I followed the HPDE/Time Trial/racing school path with POC to get my racing license which required sufficient Time Trial or equivalent advanced DE experience a plus two POC race school weekends and participation in a few races without any incidents. Then I received my racing license.
The PCA path to racing is very similar to POC but has the advantage of a nationwide racing program. When I applied to race with PCA, they accepted my POC racing license on a provisional basis but I still had to do a one weekend race school with required test sessions to demonstrate that I had the requisite skills and complete the races that weekend to get my PCA race license. I now have both POC and PCA racing licenses.
Let's imagine for a moment that you're a club racer and win the lottery and want to move up from club racing to the lower ranks of "pro" racing (like MX-5 Cup or Continental Tires series or TCA/TCB in IMSA), then you'll apply to the SCCA for a Pro license and submit your club license and summary of your experience (your racing resume) to be able to race in that series.
(FYI - the reason that I put "pro" in quotes is that the exact demarcation between amateur and pro racing can be somewhat hard to define or determine. Using the SCCA licensing guidelines, you'll need a Pro level license to race in MX-5 Cup, Conti series, or any IMSA class. With that being said, some people will argue that those series aren't really true professional racing. But that's a debate for another thread).
Keep at this path long enough and hard enough and you could be racing at LeMan's in a prototype. All it takes is time, skill, and money. How hard could it be?