In Chapter Six of Harper Lee's To Kill a Mockingbird, why are Jem and Scout separated at the end of the chapter?

In Harper Lee's To Kill a
Mockingbird, at the end of Chapter Six, Jem and Scout are separated for a
short time.

After Mr. Radley shoots at the "intruder" on
his property, the children casually and innocently return to find the adults outside
investigating the shotgun blast. The children have to make up a story as to why Jem lost
his pants—Dill is quick enough to explain that they were playing "strip poker"—with
matches, not cards—and Jem lost his pants to Dill in this way. The
adults are not thrilled with what the three have been doing, but are obviously relieved
that they had nothing to do with the shooting incident. Atticus tells his son to get his
pants and the children split up.

When Jem and Scout return
home, Jem says he must go back to the fence and get is pants or Mr. Radley will find
them in the morning and Atticus will find out what they have done. Scout is fearful that
Jem might get shot by Mr. Radley, but Jem does not want to face Atticus' wrath and
convinces Scout not to say anything.

So Scout nervously
waits while Jem returns to the fence to retrieve his pants. He comes home, enters the
room silently with his pants, and climbs into bed—still shivering, Scout notices—and
finally falls asleep. This is why the children were separated at the end of the
chapter.