You have seen it a thousand times. Students come and they go. Sometimes they train hard and consistent, other times their attendance for whatever reason is lacking. There is no better way to help student retention than a personalized note sent snail mail.
Handwritten thank you cards are what great companies and businesses do. They go the extra mile.
Just purchase a few of these Thank You cards, fill them out, write a personalized note to the student thank them (find out a little something personal and put it there), add their address, put a stamp on them and drop them in the mail.
People get really motivated when they know you care about them and what better way to communicate that than with a handwritten message. It really motivates students to keep being consistent with class.