The circuit playground is a great tool used to introduce students to programming as well as circuitry. There are several sensors on a circuit playground such as sound, motion, and light that allow for a wide variety of projects to take place. What makes this tool unique is that it is not very expensive (about $25 each) and can be used in many different ways.
Circuit Playground is a perfect introduction to electronics and programming. It combines an ATmega32u4 microcontroller with full official Arduino support and a collection of useful sensors, inputs and outputs all built-in. The board is round and has alligator-clip pads around it so you don't have to solder or sew to make it work. You can power it from USB, a AAA battery pack, or with a Lipoly battery (for advanced users). Circuit Playground has built-in USB support. Built in USB means you plug it in to program it and it just shows up, no special cable or adapter required. Just program your code into the board then take it on the go.
Circuit Playgrounds come in 2 models. The Classic Circuit Playground and the Circuit Playground Express. It is important to know which model you have as they are capable of doing different things, and are programmed a little differently.
Code.org has materials for students to learn how to code the Circuit Playground Classic in some of their computer science courses. https://code.org/circuitplayground
Microsoft Make Code can also be used to program the Circuit Playground Express. https://makecode.adafruit.com/