You really cannot use “please” without using “thank you”. The two just go together. Not using the two together would be like having a knife without a fork, a belt without a buckle, yin without a yang.
“thank you” says to the other person that you appreciate his/her effort and kindness. If you have expectations that students will work hard and will learn to be kind, then saying “thank you” I your way of acknowledging that you know they have been kind and diligent and that you appreciate what they have done for you.
End a statement of gratitude and appreciation for someone respecting your wishes with “thank you”.
“thank you” is the perfect transition; it paves the way to the next request, lesson, or task in class. It makes whatever you want done next so much better.
The most effective way to use “thank you” is to follow the person’s name:
“I truly appreciate what you did. Thank you, George.”
“George, I truly appreciate what you did. Thank you.”
Strongly consider adding the words “Thank you” to your worksheets, assignments, and other papers that you distribute in class.
taken from : Onward Effective Teachers
by Harry K. Wong
of Harry K. Wong Publications