Creepy Crawlies

Last week I found a snake in my classroom.  Yes, it was only a  little garter snake, but I don't like snakes.  At all.  I didn't want to get close enough to it to see if it was rubber so I went and grabbed my neighbor teacher.  She picked it up and it pooped on her.  Gross!  It smelled awful.  She took it outside and let it go.  She was my hero of the day.  Now, the question is, how did it get into my room?  Did it crawl up the drain?  Ewww!