If you need a simple device which can be used standalone and with computer, and you do not work with BT type of sensors, MoLab is a very good choice.
It is a small, not expensive, and easy-to-use graphic data collection system. 
It is a Windows CE device equipped with its own processor and memory, operated via a color touch screen (with stylus). It works with ML type of sensors. 
MoLab is a versatile device, which can be used in the field and in the classroom.

School Level: