Here are some corrections and suggestions to make your text sound more natural:
My school is a beautiful place on spring days.
There is a little tree that especially stands out.
When it is in full bloom, it has such a strong aroma that even a man far from the tree can notice it.
It has such a beautiful color that people often stop just to look at it. There are always people gathered around it. It is also famous for its long history.
In front of the tree, there is a monument stone* that tells the story of how the tree got there, where it's from, and who provided it to the school.
*I wasn't sure if you meant to type stone or sign your original text? You could say monument, monument sign, or monument stone.