That's when I found the Remind service. It is completely free and using it has raised my homework completion rate from 25% to about 75%. Basically, the way it works is a teacher creates a free account and is assigned a course name or number. The teacher then shares that number with students and they can text it in to become a subscriber to your class. Then, you can send out text messages (or e-mails) to them through that service via the Remind website. You can send reminders to them immediately or you can schedule them to be sent at a later date/time. The best part about this is that it offers the convenience of texting without anyone actually knowing each other's phone number - you don't know theirs, they don't know yours.
I missed a couple of days for a technology conference and I was able to schedule reminders before I left for each day I would be gone. If I am going to miss a day of school due to illness, I can send them a quick message letting them know why I'm not there and what I need them to do. It is so easy and my students are always commenting "I wish my history teacher sent us reminders".
CLICK HERE TO TRY IT OUT!