when someone greets you "Good Morning", is it appropriate to return greeting with "same to you"?
In the UK the normal respomse to 'Good morning' is 'Good morning'. 'Same to you' is possible, but is usually said in response to an insult.
PS That 'usually' was putting it too strongly; I should have said 'often'. You can use 'same to you' as a response to many good wishes. I simply meant that, in response to 'Good morning' it's common to reciprocate - rather than just respond: 'Good morning'/ 'And a very good morning to you too'... something like that.
Please note I'm not a teacher;
I often hear that phrase after some casual greetings:
A: Have a nice weekend and see you Monday
B: Same to you, bye.
If someone greets you with "Good morning," it's best to respond with a "Thanks, same to you," if you're going to use "same to you." In AmE, it seems like the most common response to "Good morning" is to simply reply "Morning" (said with a smile and a slight nod).