Why did Cal take extra care of Jet and Scout when they're going to Cal's church

if you mean jem instead of jet, cal was being cautious and careful as she wanted to prove that the negros or rather dark skinned people were just like any other white man no more no less. she wanted them to learn and benefit from it. thus she indicated to the others to be extra nice to them as she was aware that due to the past treatments by whites the negros had grown emotional and might try to hurt or speak rudely to the children though the matter did not relate to them.

but she took them to the church so that they could prove to them that they were equal or rather better than the whites by welcoming or recieving them warm heartedly so that they may have no wrong thoughts about them in their future.

if this helps i am glad.