Rather than dig through and respond to numerous posts opposing my statement, I'll say this...
Are all students and recent private pilot certificate recipients incapable of handling a 300HP aircraft? Nope, not at all. But, history and common sense prove the odds are against them. It's too much aircraft, too soon.
Yes, the Navy does it with a 1,100SHP Texan. But, those guys don't just jump into the cockpit. They spend hours in a simulator and in class beforehand.
I teach primary students in glass and it's not an easy task. We all know the fact of "an airplane makes for a lousy classroom". It is a fact and not a cliché. Thanks to our simulator it's a much easier process where that learning can be done safely and without concern of distraction.
I have some very capable students with incredible smarts and accomplishments in their lives. One has built two good-sized companies from scratch, totaling over $65 million. But, I would be selling him short if I agreed he should just jump into an SR-22 and start his training. His dream is owning that or something similar. He could buy several outright with cash.
I'm not saying it can't be done. I'm saying it's unwise to do so. If it's recommended I teach BAI for several hours along with VOR tracking and IAPs before entering clouds, why should this be any different for primary training with regard to how fast they fly?
Ever since my experience flying a few ILS approaches with the guy in his A-36 a few months back, I established airspeed limitations for pretty much all phases of flight, especially for primary students:
If you fly too fast, your errors happen even faster.
Some of those flying too fast never knew what hit them... or rather, what they hit.