The Activity Feed found on the teacher's Home tab provides immediate feedback in a real-time update when a student has completed a lesson. Each line of information contains a messaging icon and a 'star' icon.
The messaging icon allows an educator to send a quick message of encouragement to the student. See related article on Messaging a Single Student for details! The star icon allows the educator to send a 'thumbs up' acknowledgement of the student's success on the lesson.
Both options can be simultaneously used and will become visible to the student as a message from his/her teacher under the student's Message center in Think Through Math.