Hi Shifty,
Not to worry.
It happens to the best of us.
The important thing is that you made a decisive move in asking her out.
Now that she has let it be known that she only sees you as a friend, you don’t have to keep torturing yourself in an attempt to figure out whether she likes you.
So many guys who never drum up the courage to ask a girl out often put themselves in this position.
You never have to worry about that now.
As far as the message, you really don’t have to respond to it.
There really isn’t much else to discuss.
You should not react to her in any other manner than is the basic norm when you see her at school.
In other words, you can still be friendly.
However, you don’t need to spend any quality time with her at school, whether it be at recess or somewhere else, if you don’t really feel like it.
Start focusing your attention on talking to other girls and asking out the ones that you are interested in.
It will not be long before you will meet a girl who says yes and follows through.