I am currently going through literature about the use of target language in the classroom in preparation for what I think I would like to study further for my MA. I have started with a PGCE favourite, written partly by one of my course tutors, James Burch, called Something to Say: Promoting Spontaneous Classroom Talk. This book makes so much sense after having finished my teacher training, and 6 years later it is reminding me about why I do the things that I do in the classroom, such as the register routine and I have just been reading a bit about the forfeits routine which can be great fun for the pupils.
All you need is some pre-prepared materials such as the powerpoint I have embedded below and as soon as someone steps out of line and talks in English you can pull out this routine and get the whole class involved in telling them off and making them do a forfeit. The 6 boxes are trigger controlled in powerpoint, so you can get the pupil in question to pick a number rather than showing all the options.
I had a great experience of this in my last school where a pupil spoke in French by mistake (in a Spanish lesson) and consequently had to rap the alphabet in Spanish. Her friend next to her began to beatbox a background beat for her and the whole class was in fits of laughter (including me!) as this comedy duo rapped and gave the beat for the Spanish alphabet. Classic!