In "To Kill a Mockingbird", why does Atticus say Scout should ignore Jem in the treehouse?no

I think Atticus just recognises that Jem is approaching adolescence and needs occasional time on his own to think about things and figure them out. A lot is happening that Jem is picking up and worrying about more than Scout and Atticus, being aware of this, thinks the best way is for Scout to let Jem come back to her in his own time. Of course this is also part of Atticus's general parenting strategy: let children get on with their own lives with as little adult intervention as possible.