Experienced in teaching adult private students but now – a job teaching children

I live in Colombia (I’m from the USA), and have been teaching private lessons to adult business people for a bit more than 5 years. Now I have accepted a job teaching in a primary school. My experience with children is limited and many years ago.

The job is simple – get the children to talk in English. I do not have to teach grammar/reading/writing, only get them speaking. They are first grade through fifth grade and very undisciplined. The school does not permit teachers disciplining the children.

Problem is this – how do I get them to speak?

Any suggestions from anyone with this kind of experience?

Thanks,
Chip