Also, to add to my previous post, in my view less is more.
What is the point of trying to rush through 2 lessons which the children will not absorb properly at the time, never mind remember a week down the line.
My approach has always been to teach less, but firmly implant the words and structures into the pupils' minds. My pupils may have come across fewer words by the end of a term, but they can use the words they have learned with confidence. They have learned them by heart and they are confident saying them and using them in sentences. (This is my approach with children anyway).
Having said that I do introduce more vocab through the use of songs - which by the way are excellent when it comes to a large class.
There are games you can use with big classes - where the children must stay in their places, and can only whisper or they lose a point for their team - otherwise as you say, it's just pandemonium.
- make your job easy and fun teaching children English with games