For those schools doing the Junior Engineering programme (typically Years 5 & 6 in Primary School), the projects are a mixture from Levels 1 & 2. The Inter-Engineering programme (generally Year 7/8 in a Secondary School) has projects from Levels 1,2 & 3.
Level 3 projects are more advanced, take longer to build and are more technically challenging. Students who have already spent a year doing Junior Engineering should easily be able to progress to Level 3 projects. However in practice Inter-Engineering based Clubs are generally stand-alone with members new to Imagineering.
It is possible for schools to run the Junior Engineering programme for students one year and then do Inter-Engineering with them the following year. The year and termly schedules are downloadable below.
More detailed information is available for each project by following its corresponding link. On each project page you will find further documents available for download.