In Kindergarten and the lower levels of Elementary school, students learn skills like reading, writing and basic mathematics which are essential developmental skills. At that age, children have not yet developed the ability to recognize the future and how or why something is important for their future. They are drawn towards what they get pleasure out of. For these students, learning should be and can be fun. "Fun" learning will draw students towards the essential skills that they are learning and gets them involved. Additionally, for the average student, these skills are developed naturally with little effort when they are exposed to them.
Older students have different needs when it comes to teaching styles and ways of learning. They cover more advanced material that requires more than memorization, and they should need to make an effort to learn it. The exposure that fun learning provides is not sufficient in order to achieve full comprehension. They need to not only learn but understand the concepts, how they work and why they work. They should have to organize the material in a way that will help them to understand. Not only will they learn the material, but the learning that they will do will also develop other skills that are necessary to be a successful and responsible working adult, such as reading skills, writing skills, organizational skills and analytical skills.
Learning should be fun for younger students. However, "fun" learning is not a appropriate platform for older students and the more advanced material that they will cover.