It is an oak tree, and it is very old. It was a sapling when the school was built.
Can you predict what happened to the tree since it was planted a long time ago?
What was the tree like when the school was new? What is it like now? Can you predict who is looking at the tree outside the window?
The tree was planted when the school was built. Both are old. The tree has grown bigger over the years, until it is very tall, and the students can see it outside their window.