Walk into a student bathroom. Although this may not your favorite thought, you can get a good read on how well a school is taken care of by its bathrooms.
Different schools place different restrictions on where students can go.
See if students are where they are supposed to be. Don't worry if you see some children just sitting around and talking. Social interaction is an important part of a student's day, however you also want to see students doing research or engaged in an activity like yearbook, or photography, or meeting with a teacher or counselor. If a school has a dress code, see if it is being followed. Also make sure that your child will be able to be comfortable with what is being worn.