Given scene/plot descriptions from movies or TV shows, and given a specific question about the scene, summarize the question into a title

In Kindergarten Cop (1990), why are there kids above 6 learning inside a normal school? Are they special, or is something off? For example, the bad guy is searching a kindergarten for his kid, while stating his age is 6.
Why are there kids above 6 and in school

In the movie Arrival the aliens say that they will need help in 3000 years. What for? Is it implied or mentioned in the movie because I didn't catch that part. Is it mentioned in 'Story of Your Life' that is the short story the movie was based on?
What did the aliens need help for?

Apparently Scarlet Witch does have the ability to fly. She's clearly levitating in this particular scene from Avengers: Age of Ultron which I didn't notice until I watched AoU for the 4th time today. I know she has the ability to fly in the comics but why didn't she attempt to fly prior to this scene in AoU?

If Scarlet Witch of MCU has the ability to fly, why didn't she attempt to fly earlier?