Re: Youth 22LR
^^^^what greg said.
might as well get a regular sized rifle, then cut down the stock to youth dimensions, then restock later, or add one of those slip on recoil pads for instant extra LOP. the market for rimfires isn't what it used to be, there are many options is restocking now available, and you can always buy a replacement stock from the manufacturer.
i'd probably go with a savage mkii or marlin 925 (or wait a few months until the XT22 series becomes more available) with sporter barrel and synthetic stock and open sights to keep down on weight, and still have the options to add "goodies" as far as bases / scopes / stocks / drop in triggers, etc. as the kids grow. plus the mkii - 925 series base models can be picked up at walmart for under / around $225
for the single feed you desire, pick up and extra magazine or two, with one round in each. teaches some mag changes and muzzle dicipline as a side benefit.
the CZ as mentioned above has more of that "big rifle" look and feel, and IMO better shooting - but a little pricier.
the remington model 5 is also a nice rifle, . a really good shooter, big rifle look and feel. i've shot it a few times, still kicking myself in the butt for not getting one when cabela's were selling them for 180.00 2 years ago. unfortunately NOW DISCONTINUED, it'll be tough to find parts / restock if needed to.
back to the savage and marlin, if the barrel length matters you can always cut it back yourself
LOW BUDGET .22 SIL. RIFLE/TRAINER - shortening the barrel you'll end up losing the front sight, but if handy enough you can drill / tap / and install one yourself, even maybe JB weld one on.
but in the end, IMO the full sized .22 is the way to go, slightly modified for a youth now, then "reset" later as they grow.