OK. I'd have guessed a little older, but it would explain some of their mosts childish moments (like Wim pushing buttons, despite being into is clearly a life & death situation).
Fern mentions she knows of Coruscant and Alderaan, which doesn't help -- these worlds are extremely ancient. The kids do learn about them in school. It's logical -- real life middleschoolers can identify a few foreign capitals. But identifying... X-wings and associating them with "good guys"? That's quite strange. According to Wookiepedia, the Clone Wars' main superiority fighter was the Z-95 Headhunter. Incom developped the X-Wing as a candidate for the Imperial Navy. So they appeared at the earliest after the Clone Wars (19 BBY) and were a prototype. Still going with the same source, their use started to be widespread in 5 BBY and the Rebel Alliance used them in 1 BBY.
So basically At Attin might have never been totally cut off information-wise from the Republic, since their schoolchildren had access to enough material for someone interested in (or in Wim's case, fascinated by, but KB recognized them as well) the topic could correctly identify X-wings and associate them with "good guys". Which in this case must be the Rebel Alliance, since they weren't used by the Republic to win the Clone War. And they were never used by the Empire so it can't be that At Attin is just a loyal planet to the Empire -- the children would associate X-wings with terrorists if it was the case.
Is it possible that they just are following the news on TV about the Republic, the Empire, the Rebellion... and the children don't care about the news but get some pieces of information? And the information black-out is only one-way? But then, how could they miss that Alderaan was destroyed? It must have been a significant event discussed by parents. And if they had learnt about Alderaan in school, the information "and it was the first planet to be blown so it no longer exists" would have been mentionned.
He doesn't seem to be a total bad guy. Sure, he ordered the acid trap to be reset, which was meant to kill every bounty hunter/pirate, in cold blood. But he obviously had reservation when fighting "Captain" Fern. He practically begged her to yield. Wouldn't a true pirate just slit her throat and be done with that (ok, that and because it's a Disney 12+ series)? SM-33 wouldn't have objected. Also, he seemed to genuinely care when Wim brandished a lightsaber, despite having no responsability if Wim had chopped his own arm's off...
I could see Jod defending At Attin against the pirate... But is At Attin in need of defending? The children knows about starfighters and spaceships. It is strange to learn about that unless there is a fleet (a droid fleet, maybe) that they could be familiar with.