I'm a teacher mummy running an Eye Level Centre in Sembawang. I agree that home tuition can be convenient but might not be effective. Children realise they have home turf advantage and will not hesitate to leverage on this. So having a less familiar environment can affect their attitude. Boys especially excel with competition.
I think small group enables your child to harness the power of the group i.e. sometimes they may be reluctant to ask what they think is a silly question, but when another child asks they learn together, without the teacher being overwhelmed by the pressing needs of a full class.