The correlation coefficient measures the strength and direction of a linear relationship between two variables, in this case we have the number of students attending drama club and the number of students attending poetry club.
This coefficient is known as "r" and its value is always between +1 and –1.
The more close it is to -1 or +1 the stronger the relationship. When r has a value of 0 it means there is not relationship between the variables.
The given r value is -0.36, it is more closer to 0 than to -1, then the relationship is weak, it means there is not much expectation that one variable cause the other to change.