What does it mean when my crush puts her head on my shoulder?

So one day before class started I was standing around and my crush walked in and we immediately started talking then after that I had to do something when I finished it stood by the corner of the classroom and like spacing out then I felt something on my shoulder and when I turned around I saw my crush's head on my shoulder. She came up to me out of nowhere and put her head on my shoulder. In the past we would make jokes and she would tease me all the time I even gave her a side hug on her birthday. I never had a girlfriend so could someone please tell me what could this mean?