To determine how many students from the math club went to the soap box derby, we consider the information given about the vans.
Each van holds 6 students and there are 2 vans. To find the total number of students from the math club who went to the derby, we can multiply the number of vans by the capacity of each van:
\[ \text{Total students from the math club} = \text{Number of vans} \times \text{Capacity of each van} \]
Substituting the values we have:
\[ \text{Total students from the math club} = 2 \times 6 = 12 \]
Thus, the number of students from the math club who went to the derby is \( \boxed{12} \).