Looking at colleges in 6th grade is awesome! DD started talking about colleges about then and I wish we had worked more visits in earlier. To go on a college tour you just sign up on the website and go--no age or grade requirements. You can schedule it for summer or during school breaks. You will get a different flavor than the "overnight" stays offered to High School Juniors, but it still gives you a look at the general vibe of the school. In 8th grade we found it helpful to look at the requirements for enrollment at different universities, and different majors, to plan high school classes. If your DD will be taking high school classes in middle school, the middle school classes should be included in the planning. If your local high school has an awards night, you could attend it during 7th and 8th grade to get a feel for the achievements deemed noteworthy.
