This activity is going to require you to know the temperature of your class, as it were. If it's a class with any underlying tension or conflict between students, then it's probably best to skip or modify this activity. If they generally get along with each other then you should be okay, as long as the teachers keep an eye on any student likely to be mischievous.
First, I tell the students that in the US (my home country), usually boys give chocolate to girls, and there's no White Day at all. In schools, many students give each other Valentine's Day cards. It's just a kind thing to do, and not always a sign of - perish the thought - romance!
I pass each student one copy of the paper and ask them to write their name on it. Next I draw a big snaky line on the board that corresponds to the layout of the desks in the classroom. The idea is that students will pass papers to the desk in front of them, or behind them, or next to them, in an order that will constantly lead the students to continually receive new papers that aren't their own. To be honest, I can never explain this very well, so if you have any good strategies, please leave a comment!
Once the passing scheme is worked out, I have them pass their papers to the next person. I tell the class that their job is to write something nice about the person on their card. I write a bunch of examples up on the board, depending on what grammar they've studied. For example:
- You're cool!
- You make me happy!
- You are really good at _________!
- You're friendly/cute/handsome/funny!
- Thank you for ______!
I emphasize to the students that the message absolutely must be kind - I don't ask them to sign their names, but if you're worried about accountability, you can have them do that if you feel it's for the best. If they absolutely can't think of anything, they can draw a heart or just not write anything. After they're finished writing, they pass the paper to the next student in order. In the beginning I might give them a minute per paper, but as the students write messages a couple times, they'll begin to do it faster so you can speed it up. Run them through as many rounds as make sense given the time you have in class. Once you feel like it's time to finish, collect all the papers and pass them out to their original owners.
Some students can take a little ribbing from their friends, but some might be the subject of some negative messages, so that's why it's really important to know a class well before trying this. Ideally they'll feel good after having received a lot of compliments from their classmates. I often circulate one for the class' homeroom teacher as well and leave it on their desk.