They do not limit themselves to people their own ages. All three are in swim lessons and we get together regularly with friends we've made through play group. Whatever interest they have at the moment leads us to locate resources to help them. The misconception that many people have about homeschooling is that you HAVE to use a pre-packaged curriculum. For most people, it is too confining to accomodate true learning.
Libraries have a wealth of useful materials available.
If you look, you'll find what you need. Because my children choose their own things to learn about, they stick with it until they are satisfied. They learn more about it because they are truly interested in whatever they have chosen. And they each end up getting interested in what the others are doing and share the information as well. All three have learned a lot about constuction vehicles because my youngest son has taken an interest in them.