In Star Wars, Luke Skywalker murders an estimated 250,000 civilian employees aboard the Death Star. The same source says there were over 1.5 million troops aboard who we learn from the sequels are not all evil – many have a moral compass, disagree with the Empire, and can be turned to the "good" side.
But despite this instantaneous mass-murder, there is apparently no "disturbance in the Force, as if millions of voices suddenly cried out in terror and were suddenly silenced." Maybe those people's "souls" did cry out but Luke is so hopped up on shooting the ball through the hoop as the timer ran out that he didn't notice…? Maybe Luke's Force powers don't include empathy, just target accuracy?
Compare to Buffy The Vampire Slayer where enemies conveniently dissolve into sand when killed, and Star Trek: TOS where phasers cause people to disappear along with their clothing and accessories, but do not dissolve walls or leave even a scorch mark on the floor.
The story ignores it and moves on.
There are no consequences and young people are not so critical as long as they are entertained. There is a "safe zone", like the game of tag. When you are off-base the monsters can chase you, and that is the fun part, but when you get back to home-base you are safe. The peril can be terrifying, but in the safe place it cannot touch you. There is a clear distinction between un-safe and safe.
In contrast, I still vividly remember watching "Star Blazers" (actually Space Battleship Yamato, dumbed down for American syndication) and feeling shocked by the death of a main character. It broke the rules of cartoons, it broke the rules of kid's shows – I was pretty sure it broke the rules of every adult American TV show I had ever seen. It felt edgy. Real. Different! I had been suddenly thrown out of my comfort zone and – I recall vividly – my expectations for storytelling changed on that day forever.
I thought about that death for weeks – not because "boo hoo, I am sad he died", but because it felt like a revelation in what could happen. I became obsessed with anime (imports were still rare then), and found out the show I was watching wasn't even the real story…. 40 years later, this is still something I remember as a life-changing event. A total eye-opener. Bad things can happen that cross into the safe zone. Stories that pretend otherwise are for "babies". Star Wars was demoted to a puppet show. Star Trek became campy space women. I couldn't take them seriously anymore (I kept watching, but wishing they had more substance).
You can probably play it both ways.
Your characters can be terrorized, screaming and running from horrible monsters, but so long as they make it back to "home base" the tension is released. Mass-murder on incomprehensible scales can be committed by the "hero", but as long as there are no bodies lying on the ground: ¯\_(ツ)_/¯
But this is also an age where a meaningful death can actually start to have some consequences. Kids know the pattern by this age. They've seen plenty of shows about a group of kids who go on adventures and save the universe. They are expecting easy villains and hollow triumphs that are about "shooting the ball through the hoop as the timer runs out". Be willing to break the cliché, and you might open their minds to a lifetime of better possibilities.