I think I can see spirits/ghosts?

This happened once in 2nd grade. We had sport on and while we were getting put into groups my friend looked down the bottom part of the school playground (there's a giant slope in it thats called the 'bottom playground') and asked me if I could see what looked like 2 people walking up, but they were completely white and almost transparent. Once all the groups were sorted everyone went down to the 'bottom playground' (where me and my friend saw the spirit) to play baseball. While my friend was taking her turn I swear I saw something crawling towards me. After sports was done my friend was laughing and telling me how it was a prank but it didn't feel funny.
Today I told my mum about it and she told me that the school used to be an asylum but was then closed down and turned into a school.
I also have some experiences with hearing voices and shadow people. Everyone calls me paranoid, am I?