I'm on the ladder with this one. What are your opinions about a strict "English-only" language policy in the classroom? I teach ESL classes to Spanish speakers and find that they constantly talk in their first language to one and other. I speak Spanish and find that they frequently speak to me in Spanish although I continually ask them to speak in English. What are some ways to enforce such a policy? Thanks.

You could fine them a small amount for every Spanish word they use. The proceeds could then be used to go towards the cost of a monthly lunch meeting, or even a Christmas party. If they are really bad offenders, you could use the money to take the class on an excursion to Japan - where almost nobody understands Spanish!
Students: Are you brave enough to let our tutors analyse your pronunciation?
Do you have any Post It Notes? You can "ticket" them every time they speak in their native language. Believe me, after you have ticketed them 2-3 times, they stop speaking their native language.

When I use this technique, I announce that they are getting ticketed and stick a small post it on their shoulder or arm. It's embarrassing for them, but not insulting. Everyone gets a good laugh.

Sometimes low level students do need some explanation in their native tongue, if that's the case you could assign English only groupwork and require them to speak English only during those tasks. You can ticket them during that time.

I do not teach ESL, I teach in a trade-school. For many of my students English is not the first language. Other teachers want a "English Only Policy." There is nothing written so I do not enforce this. But I have to say I get a very bad feeling every time I hear about this. Why should I limit the side talk to English? If they are bonding, why should I interfere? I have no fear that they are talking smack about me or other students... which is the most common reason given for English Only. I find it to be culturally insensitive... and just kind of pointless. I lecture in English, projects are written in English, who cares about conversations, side chat, or god-forbid a Spanish speaking student explain the assignment to another Spanish speaking student in Spanish!