In this regard, can you have a high IQ and be bad at math?
It is absolutely possible to have a very high IQ without being good in math. To believe that one must be good in math in order to be very bright is very limiting.
Also Know, can you have a low IQ and still be smart? If the test doesn't misfire for reasons like those mentioned above, the answer to your question is no — someone with a low IQ will not be very intelligent. IQ tests don't measure every aspect of intelligence, but they do a pretty good job of measuring general fluid intelligence, which makes up the bulk of it.
Consequently, does IQ correlate with grades?
Unfortunately, they are not. Grades measure your performance in school, while intelligence measures your performance in life in general. You might know yourself that in school, you are given the material then tested on it. But in life, you are given the test first.
Why am I smart but get bad grades?
Bad grades aren't always because your child doesn't understand the material. In some cases, when students aren't challenged enough by the material it can actually lead to poor grades. Some students simply don't test well, no matter how smart they are. Many of these students suffer from what's called test anxiety.