All of our field trips have some kind of educational value, and mostly they are to do with the unit that we are teaching - if we are learning about fire safety then we go to the firestation. As for how many trips it all depends on what we are learning about and how far away things are from our school. If we can walk there and it costs us nothing then we are more likely to go. If the unit we are learning about does not inspire any field trips then we won't try to invent them. We are allowed to go on as many trips as we want, but we have to be realistic about money, time out of class, and the value for the children.