SMS, or text messaging, is by far the most wildely accessable interactive communication platform in the world. There are approximately 5.3 billion mobile phones around the world. But only about 30% of them have the capability to connect to the internet or receive data. At the same time, nearly 100% of mobile phones - even really old ones - can receive and send SMS messages. Yet despite its huge level of adoption worldwide, text messaging is not used often for teaching and learning. All you need to get started is a tool for managing sending and receiving SMS messages, and a service provider to send the messages for you.
Fortunately, there is a great little piece of free software for managing SMS messages for educational organizations called FrontlineSMS. The software runs on Mac or PC and allows you to send messages and set up automatic responses to text messages you receive in just minutes. This could be used for communication with students and parents, and even for assessment purposes.