Three tools that every STEM teach interested in teaching making to their students should have.
A 3D printer used to be a something expensive. But now they are very affordable (almost $300 for a kit.) 3D printers are a great tool for teaching engineering because they actually let students invent completely new things without really having to worry about manufacturing. A 3D printer can create anything so they leave many more options for students than the standard click-and-snap kits like lego.
3D printers are especially useful if students are learning CAD, because it helps them understand how a visual, but abstract design, actually looks and feels in the real world when it is created.
The 3D printer is also ideal for teachers who want to just have more diverse projects and assignments. Since there is really no limit on what they can make, they are a much better investment than single use machine tools.
The Arduino is a microcontroller that allows students to learn to program and work with electronics. The Arduino is easily the best platform because there is a huge support base for it. Literally any question that a student has there is a tutorial or forum available with an answer.
The Arduino also supports various levels of programming experience. Beginners can use graphical block programs like Scratch to program an Arduino, and more advanced students can program directly in C. Then even higher students can learn to control the Arduino from a computer using Python. (Though that is generally at the High School Level.)
If you are able to have machine tools as part of your class you should consider a bandsaw. Bandsaws can create almost any kind of cut ranging from a straight line to to a circle and curve. They are also relatively safe. It is difficult for a student to be in danger of losing a finger on a Bandsaw.
The bandsaw is also very versatile in what materials is can cut. Your students can cut plastic, wood, or metal on a bandsaw and have no problems.