Imagine that the question asks "to what extent do you agree or disagree?". Can you see the problem in the type of essay outlined below?
Introduce the topic, then answer that you completely disagree
Give the other side of the argument e.g. "On the one hand, many people believe..."
Give your side of the argument e.g. "On the other hand, in my opinion..."
Summarise the reasons why you disagree
Many students make the mistake of writing their "agree / disagree" essays in this way. Can you see what's wrong and where the problem is?