ISO 80000-2:2009 is a standard describing mathematical signs and symbols developed by the International Organization for Standardization (ISO). In teaching mathematics, should one always follow this standard?
As an example, there is no universal agreement on whether zero should be considered as a natural number or not. But since there is an international standard which considers zero as a natural number (though the teacher may not like this convention), should one teach base on this standard only in order to avoid any confusion?
Another example is, people use $\log x$ for both natural and common logarithm. In my teaching I usually spend 10 minutes explaining the difference and the fact that in most calculators, $\log$ means common logarithm and in WolframAlpha, $\log$ means natural logarithm. My personal rule of thumb is, $\log$ means natural logarithm starting at pre-calculus and means common logarithm before pre-calculus. Based on ISO 80000-2, one should use $\lg$ for common logarithm and $\ln$ for natural logarithm. Under this convention, ambiguity ceased to exist.
Edit: The Chinese goverment published a standard in 1993, requiring all institutions in China teach that $0$ is a natural number. So at least in China, the dispute is forcefully solved.