Hi Maggie-
A tablet may, or may not, know where you are depending on where you are and the type of tablet. All modern cell phones are required to contain a GPS which receives signals from GPS satellites and so is able to triangulate your location as long as you are somewhere that you can get a signal. Many tablets, and all those with cellular capability, contain the same type of GPS and can determine their location whether they have a data plan or not.
However, if you are using an iPad that is WiFi only, which is the type available in most schools that use iPads, the ability of the tablet to determine your location depends on your being connected to the WiFi network. (There is location information associated with the WiFi router.) Once you go into the field and off network with these types of iPads (or other tablets that lack a GPS chip) your ability to locate depends on you "knowing where you are" and being able to "GIS-guess" your location on the map aerial image.
Ina