I have recently supported two primary schools in County Durham to put on a science fair in their school. I worked with the year 6 pupils over four weeks to help them take charge and put on a great show for their peers. In the first couple of sessions, I took lots of short, fun activities for the pupils to try. They critiqued them, changed some, chose some, added new ideas and rejected some until they had their own repertoire of activities for their fair.
In each school, we ran a half day science fair for key stage (KS)1 and a half day for KS2. A small group of 2-3 year 6 pupils were in charge of each activity and demonstrated it to their peers in the rest of the school. We opened each fair with fizzy drink and mentos fountain which got everybody excited and then pupils went round the different activity stations and were helped to try the activities themselves by the year 6s. In one of the schools the year 6s trained the year 5s to demonstrate the activities at the KS1 fair. We also had other teachers, parents and governors helping out during the day.
Everyone who took part had a great time. The kids demonstrating the activities really got to understand the science behind their activities so they could explain it to their friends. Parents were also invited after school to see what had been going on so the project was also a great way of getting the wider school community involved.