There are a number of reasons for setting up shelters when you arrive at a forest school site. Firstly, often you arrive with a variety of kit and individuals will have their own personal belongings, these items need protecting from the elements. You will also need to keep yourself dry and protected, if built correctly your shelter could also protect your fire area, allowing you to keep warm as well as dry.
An essential piece of kit is your tarpaulin. This can come in a variety of different form, either one purchased specifically for the job, a groundsheets or any sheet of plastic of a decent size and thickness. Below you will see some examples of how your tarp can be set up. If you want information about how a specific tarp is set up then click on the image.
Picture Reference 
When you are out in the woods you can build shelters without using a tarp and this can be a great fun activity for both adults and children alike. They come in all sorts of designs and need to be adapted to the areas and materials around you. Often you will find their shape will mimic those of the shelters made with tarpaulin. Shelter made from sticks can be made water proof with the learning on materials over the top. This layering depends on what is available, I have found bracken covered with humus to be effective. See some examples of shelters built below.