It was interesting to see how you decided what we meant by "size". Kelsey from Sutton Primary School (with the help of his cousin Michaella) measured the length of each shape at the longest point (I am guessing that he printed them off first). He says:The order is green ($11$ cm), red ($12.5$ cm), yellow ($13$ cm), blue ($13.5$ cm), orange ($15$ cm), purple ($16.5$ cm) and lastly grey ($18.5$ cm).
Louise and Rosie from Fulford had a different strategy. They wrote:We observed the area of each and tried to rearrange the shapes in our heads to compare them. This is the order in which we think the shapes go: (smallest to largest) Green, Purple, Red, Light Blue, Yellow, Orange, Dark Blue.
So, Louise and Rosie have a slightly different answer from Kelsey, but more importantly, they each explained how they tackled the problem.
Thomas from St Peter's had a different strategy again, and a slightly different order:Green, Red, Purple, Yellow, Blue, Orange and Grey the same size.
Perhaps you found a different way again to measure "size"?