Follow the given steps to create a chat room for yourself:
Login to your Student Account
Click on "Chat Rooms" tab on the Home page
On the left column in the chat room, click on (+New) sign and "Create Channel" to create new channel
Type in the name of the new channel
Add a short description of the channel
Add your friends and teachers you desire in your channel (You can also make a private channel)
Click on "Create Channel".
After your channel is created successfully, type in your message and send it to your class.