Two teachers are in a school of primaries 1-6. One to three in a room and four to six in the second class room in a village school. How will they teacher these clusters effectively.
The answer to this question is massive and many teacher struggle in achieving success. I would start with understanding the learning needs of the students and plan for their needs. It maybe that you will need to alter the groups based on social dynamics (group theory and soft skills) or current learning levels (differentiation and scaffolding) and specific learning needs. It will also depend on the content which the students need to cover.
Then consider planning and resources and up-skilling (training) the teachers. Also, consider, it maybe not be related to the inadequacy of the teacher(s). I have attached a link which may help: http://dancampbell.co.uk/visualising-importance-learning-objectives/