Young children's "chapter books" don't use passive writing. Like, at all. There aren't many ing words. Almost all the verbs end in ed, making the action immediate and strong.
The author stays on point during an action sequence. She doesn't veer off into description or narrative--unless it's something simple like, "Jack was scared."
All the sentences are clear and concise. These are for early-ish readers so the language is meant to meet their reading level. This means it gets choppy at times, but I think that's normal for the age the books target. There's brilliance in the simplicity. I, and adult, don't feel bogged down by the repetition or the lack of fanciness.
A new idea is introduced once, then it is dropped until it becomes relevant later. This is interesting because a lot of adult fiction writers continuously repeat themselves to make sure the reader doesn't forget a key point.
There's no back story or info dump. When we open a new installment, we don't get pages and pages catching us up on what Jack and Annie have been doing since our last encounter. The most we get is something like, "Jack and Annie left their swimming class and headed to the tree house." The fact they take swimming lessons might come into play later if the plot calls for some intense swimming, but the information is dropped quickly and left alone.
The story always starts with the characters heading to their tree house, not days before, not hours before. We don't see them at school or having dinner with their parents. The books starts where the story does.
Writers are supposed to read in order to hone their craft. But it's easy to get lost in the language, complicated plot or depth of characters in adult fiction. Seeing the forest from the trees can be difficult when we're so deeply engrossed. I'm not suggesting writers quit reading novels, but if you're needing a refresher on the basics, pick up a children's "chapter book," like the Magic Tree House series, and pay attention to plot structure, the active writing, and the clear action/description.