'Wow' is a teaching tool. It is not just a way to grab attention but, correctly used, a means to enhance children's understanding and improve retention. Wow leads to why. In this why state pupils experience the 'vacuum of ignorance': they know they don't know, they know that the teacher does know (usually) and they want the teacher to fill that gap. The key point is that now they are pulling the learning out of the teacher rather than the teacher pushing it in. However, wows are often misunderstood, which breeds misuse and abuse. For example, grabbing a quick attention hit with no educational purpose creates a classroom of distracted kids hyped up to the ceiling. Such gratuitous waste of wows generates well-deserved criticism. Conversely, a well-used wow can drive analysis and reasoning beyond ordinary expectations, ignite excited questions, enrich discussion and crystallise deeper understanding. It can anchor the recall of facts and concepts for years, even decades. It all comes down to the how of wow. In this article, Tom Pringle explores the use and abuse of 'wow' in the classroom and suggests why using the wow is not as straightforward as it may seem.