In many classrooms (and I include mine in this generalization), opportunities for academic student talk often end up with students speaking in parallel at an escalating volume.  When I ask students to turn and talk about what might happen next in a story we're reading, one student might turn to a classmate and say what he thinks, his partner might then make his prediction, and the "conversation" would be over.

In order to make student talk more productive, many teachers post a chart on the wall that lists "Rules for Accountable Talk," containing the conversational tricks that adults use: "I agree with you because...," "I disagree with you because...." "What do you mean by that?" and "I see what you mean, but..."  I've seen these phrases work in certain classrooms, particularly ones where students have heard actual people saying these things.  They tend not to work so well in classrooms like mine, where students mainly hear Spanish at home and where, for those who do hear English, they tend not to hear it spoken this way.  Students in this kind of classroom can certainly pick up these tricks, but they need to be taught how to use them in a more explicit way than just seeing them posted on the wall.

Here's one activity that teaches "I agree" and "I disagree" more explicitly and that I plan on including in my final project:
1.  Divide students into pairs and name Student A and Student B.
2.  Give each student 3 wooden blocks of different shapes and a paper plate as a building area.
3.  Tell Student A to put down one block on the plate.
4.  Explain that Student B now has two choices: leave his partner's block where it is and add a new block to the piece, or move his partner's block..  He can say, "I agree with you and I'll put my block here."  Or he can say, "I disagree with you because I think it looks better here."
5.  Explain that Student A has to accept whatever Student B does with the blocks, at which point Student A can make the same verbal choice as Student B.
6.  Students continue taking turns placing blocks until they have used up all 6 blocks.

The idea here is that the blocks become a metaphor for a conversation, in that a successful conversation is a series of utterances in which each utterance responds in some way to the one that preceded it.  This activity also gets at the notion that a good conversation is organic and doesn't necessarily have a predefined objective (your partner may move the block you originally placed and that's OK).  This stands in contrast to the mode of parallel statements that many children (and some adults!) easily fall into, in which one conversation partner's speech has no bearing on the other partner's.  Obviously there are more conversational tricks than "I agree" and "I disagree," but it's a starting point.  After leading this activity several times, the teacher would then make the metaphor explicit by asking a question that students have to answer with a partner and reminding them to speak and act just like they did when they were building with blocks.