In the book Freak the Mighty, Gwen sent Freak to the back yard because...?

You didn't specify in which chapter this takes place, but
I assume it is at the end of Chapter 3. Max has just helped Kevin retrieve his
ornipthopter from the tree, and he invites Kevin back to visit the down under--Max's
basement bedroom. Max wheels Kevin in his red American Flyer wagon, and they head
downstairs. Kevin tells Max about his mother, the Fair Gwen, and talks about King Arthur
and his magical sword, Excalibur. When they hear Gwen calling for Kevin, they head
upstairs. But when she sees Max, Gwen grabs Kevin, carries him up the stairs, places him
in the wagon, and "almost runs home." Kevin's mother does this
because she is shocked at Max's size and is always worried about Kevin. Max decides
that

It's
pretty simple, really. She's scared of
me.

Gwen apologizes later,
and Max finds out that she was good friends with Max's late
mother.