Why did they never finish a sentence when reading aloud in the classroom

Was there just something wrong with my subtitles or when the children read did they read part of a sentence and then start another sentence as if they'd finished the previous one? I could not figure out what this meant or why it was happening. It drove me nuts.

I can't remember exactly how it went so I will make up an example (stolen from Wikipedia):

The Pyrenees are a range of mountains in southwest Europe that form a natural
They separate the Iberian Peninsula from the rest of
For the most part, the main crest forms a massive divider between
The Crown of Aragon and the Kingdom of Navarre have historically extended on both

Did the director deliberately interrupt the flow of these readings so that we wouldn't take in any of the content from the textbooks as having meaning in the film or in the children's lives? Or were the subtitles cut off at the bottom of my screen and I imagined this entire phenomenon?