Park in Tall Oaks Court and walk across South Racine Avenue to the school. DO NOT PARK at the school itself. Police monitor the roads and will arrest any car that appears to be investigating the site. You should be able to see it easily on Google Maps, but if not, the coordinates are 42.947797, -88.15724. The easiest door to open is the one around back across from the Spongebob graffiti. If it sealed by the police occasionally, but there are so many trespassers that it is usually cracked back open before long. If there is a rock or other large object in front of the door, it means there is no one inside because someone had to place that object there from the outside.
Navigating the inside
There are three floors, only two of which I have explored. When you first walk in, you can either go up the stairs or down the hall to a door. This door doesn't open. It leads to the basement where a local cult practices human sacrifice. Don't go that way.
The staircase should take you to the rest of the school. There is a gym, two levels of classrooms, a cafeteria, etc. If you're lucky, you'll find some cool artifacts from when Prospect Hill was open. If not, you'll still be scared out of your mind. Keep an eye out for my name written in graffiti.
Because the building was so dangerous, it was closed in 2007. It can't be that dangerous, though, because it's still standing - 9 years later.
Have you been to Prospect Hill? What did you think? Leave any tips of your own or observations in the comments to help other explorers!