Arithmatic, calculator skills, basic understanding of ratios.
Assign meaning to values that are listed in metric units. For example, a student will learn that 38ºC is hot, and that 101,000 Pascals is not a large number, but merely 1 atmoshpere.
Text of Learning Exercise:
Begin with standard units of length, area and temperature. Show comparisons on the board. Introduce new measurements as needed. This can also be used in English-Language Learning classes to teach American units to students raised on the metric system.