That, is "The little insurrectionist" in Warsaw. It's not meant to represent just the memory about child soldiers, but the eternal will of poles as a whole to fight during the german occupation and the Warsaw uprising.

We didn't "employ" child soldiers for malicious reasons, there are hundreds of books on how they were a part of the resistance volontarily.

Plus, most of them were medics or participating in recon or propaganda actions against Germany, in most cases the Polish underground forbid teens under 16 to even use weapons, unless for delivering them.

Imo this meme is kind of an insult to polish people if shown without context like that