Children are at school and )
Children are chatting (with one another) in the schoolyard in the picture.
Children are chatting (with one another) at the schoolyard in the picture.
=>Are the above sentences both correct with the same meaning or is there any slight difference between them?
I suppose, both are correct and I feel in as more common than at in this sense but I'm not sure in it

Chúng ta chỉ nói at school và in the school yard
Chúng ta cũng có thể nỏi at the school yard khi chúng ta tới đây từ nơi khác (ở ngoài khuôn viên trường)
Còn khi chúng ta ở đó rồi thì chúng ta nói in the school yard

in