Platform for robotics class

Looking for advice for classes of G3~G12 kids.

There will be entry, intermediate and advanced level. Entry level will focus on basic knowledge and skills, fun and easy to start with, code block interface, plus basic 3D printing exposure. Intermediate will involve more complex task with multiple sensors and controls, coding, mixed with other classes like soldering, electronics, 3D design, etc. Advanced students will create their own projects using knowledge at college or graduate level.

Ideally there is a platform that fits all levels but if not possible, something that works for both entry and intermediate level would be great.

Key criteria:

  • Availability (not only on robotshop but ideally Amazon and other shops)
  • Affordability (entry level <US$200-300, intermediate <US$500 on top of entry level investment)