There is a scene where a child character must undergo emergency surgery without medical professionals. There's another scene where a different child is knocked unconscious and it's not immediately clear if he's alive or not.

There's some bloodless fights between the children.

Some minor name calling and verbal insults.

The children are put though dangerous situations that could potentially kill them and adults aren't around to help.

This series has much higher stakes than a lot of other kids shows. There are many thrilling and stressful scenes that may be too much for younger kids. The series also isn't a comedy, so there's little to lighten the mood in more intense scenes.