Boogie, If you're a 1911 or one of the Sigs shooter, you might consider one of the .22 LR upper assemblies. I have them for several of my guns: Two Ruger 1911's, and a Sig P226. The Sig units are about half the cost of a new gun ~$350 for the Sig branded unit. For the 1911's there are units by Marvel, Ciener, Colt & Advantage Arms to name a few. All of the above are superbly accurate, much better than the original caliber guns in fact.
There are several advantages to this course of action: first, you have the same trigger, grip and feel of the gun to work with. Giving you a great understudy on the bigger caliber.
Overall cost is the 2nd advantage...they're cheaper, generally, than an entire new gun. And I can speak to the accuracy...the above units I mentioned, with the exception of the old Colt "sliding" chamber model, are accurate enough for all but the most demanding NRA Bullseye competition.
The last point is that with that .22 unit in place, your center fire gun's weight is substantially less...making it that much more adaptable to a young person's strength, but still retains the trigger, feel and accuracy that you need for effective training. In truth, I'd use mine more if .22's were less expensive...as I cast my own bullets, I can actually load 9mm & .45 ACP for less than .22LR!!
My units have been nearly 100% reliable if kept clean...ie. the barrel breach face, bolt face and chamber area. And all of them use CLP on the rails vs. the weapons grease I normally employ with the center fire uppers in place.
Here's a pic of one of mine on a Ruger SR1911. This is a marvel and the target was shot with bulk, Remington Golden .22 solids. It's a good option if you already own one of the center fire guns.
Best Regards, Rod