Adafruit boards and MakeCode are a powerful combination. They meet almost all the needs of students getting started with physical computing.
But if you're curious about comparable boards by other makers, here's a quick look at three that are also popular with educators.
Many projects designed for other boards can be adapted fairly easily to work with the Adafruit Circuit Playground Express or other Adafruit boards.
Makey Makey by JoyLabz is an Arduino-based board that lets you use conductive objects as keyboard keys. Unlike the Circuit Playground Express, you don't have to program it. All you do is plug in the USB connector into a computer and it's ready to go.
You can use the Makey Makey to run any kind of program your computer runs, as long as it can be controlled by the keys available -- up, down, left, right, space, and mouse click. (The back of the board has connections for additional keys.)
Because it was designed by some of the same people who developed MIT's Scratch, it also works very well with Scratch programming. The latest version, Scratch 3.0, has its own Makey Makey extension.
If you want to build a stand-alone project that doesn't need to be connected to a computer, however, the Circuit Playground Express is still your best bet. The Circuit Playground Express capacitive touchpads are also a little simpler to use than the Makey Makey keys, which have to be connected to ground (marked as "Earth" on the board) to activate. And the Circuit Playground Express is about half the price.
And you can also use MakeCode to program a Circuit Playground Express to trigger keyboard keys. And input -- touchpads, buttons, or sensor readings like shake or light -- can be used to trigger a key. See the Make It a Keyboard guide for more info.
The BBC micro:bit falls somewhere between Gemma M0 and Circuit Playground Express in both functionality and cost. It works with MakeCode and has its own Scratch extension.
It can measure tilt and light and receive input through touchpads. Its output is a matrix (grid) of red LEDs that can be programmed to display icons, scrolling text, and data on a graph. But it doesn't have a built-in microphone or speaker or multicolor LEDs.
However, with Bluetooth capability, it can send and receive signals from other micro:bits and from a smartphone.
In the time since it was first introduced to students in schools throughout the United Kingdom, it has developed a large following. Educators around the world have been creating teaching materials and projects. There are also many kits and accessories made by third parties that use the micro:bit, such as the MiniMu musical glove.
However, while Circuit Playground Express is more expensive, it includes accessories you have to buy separately for micro:bit, such as a speaker. It's easy to adapt MakeCode projects for micro:bit to work with Circuit Playground Express. And Circuit Playground Express Bluefruit, coming later this year, will have Bluetooth radio communication as well.
Chibi Chip from Chibitronics is designed specifically to work with paper projects. It's made by the same people who created the peel-and-stick Circuit Stickers, the easiest way to attach lights to paper art.
An optional clip clamps Chibi Chip right onto a circuit made with conductive tape, paint, or other material. In fact, the Love to Code Creative Coding Kit comes with a book that lets you clip Chibi Chip right onto over the illustrations to complete circuits while you learn.
You cab also get a Chibi Scope with a display screen that can display text, voltage, and more.
Chibi Chip works with MakeCode, and connects to the device you're programming on with an earphone-type plug. That actually makes it possible to write code and download it directly from a smartphone or tablet with an earphone jack!
If you want to use Circuit Playground Express or Gemma M0 to create paper projects similar to those made with Chibi Chip, you can attach conductive fabric or foil tape directly to the Adafruit boards' touchpads.