I have been using Blender (an open source 3d animation package) for several years in school and it works great. It can be tricky to get started, but it's free and there are plenty of ways to create literally anything that you can imagine - from pre vis models in product design, to vfx and even 3d games. On these pages you'll find lots of useful stuff to get you started - why not head over to the model page to see how to create your first 3d mode from a simple drawing.
In school, I use Blender versions 2.49 and 2.65 - I'm mostly using 2.65 which you download by clicking the picture opposite (choose the .exe). Please get in touch via the contact pages if you would like training at your school.