19 September 2016 Last updated at 07:50 BST
They used recyclable materials such as shoe boxes, plastic packaging and egg boxes to make them.
They went to see how a team from Swansea University are building a real classroom for the future, whose aims are the same.
Their classroom is designed to be energy positive - that means they don't have to buy electricity and they have solar panels that use the sun to power them.
Kids in Swansea have been showing us their designs for buildings for the future, which they say should be as energy-efficient and kind to the environment as possible.