The examiners' band descriptor sheet states that a band 7 essay "presents a clear position throughout the response".
A "clear position" means that your opinion must be clear (if the question asks for it), and "throughout the response" means from the beginning to the end of your essay.
For this reason, it's a bad idea to save your opinion for the conclusion. We don't like 'surprise conclusions' in English academic writing. Instead, you should state your position in the introduction, support it in your main paragraphs, and repeat or summarise it in the conclusion.