According to Google Sketchup’s own website with it “Model anything you can imagine. Redecorate your living room. Design a new piece of furniture. Model your city for Google Earth. Create a skate park for your hometown, then export an animation and share it on YouTube. There's no limit to what you can create with SketchUp.”
Using Sketchup in education is getting very popular. Imagination is the limit. It can be used with equal benefit for kids of all ages. Here is a gallery of work of different students from around the world. You can find a small list of ideas for using sketchip in education from here. Get some inspiration for using sketchup in education from here. Find some fun projects in design, science and maths to do in sketchup from here.
Though Sketchup is not a difficult program to use, still first timers and those who haven't used a 3D program before may feel at sea. Below is a list of some free resources (videos and books) to get you started with sketchup.
We have been using sketchup recently in learning about symmetry and tessellations. You can download the lesson about symmetry from here and the video about teaching tessellations from here. Please note that these lesson and videos are just to get you started, customize them according to the age of your pupil.