It's much more important that people feel like they have learned instead that they feel like they are having fun learning.
The target of comprehensive school and upper secondary is to teach people as much about different things as possible, have them learn social interaction and a small amount of how to learn and how to adapt information. They will likely not learn as much and as varied information ever again.
The target of a university education is to have people learn how to learn, do research and apply that information, and drill into a single field and learn about that field and make progress in that field.
Mixing "fun" into this is counter productive for the most part.
I've seen bored kids in class, not understanding a lesson, and not caring. They're doodling away, and interested in graffiti. If I could, I'd put such a kid in a calligraphy boot-camp, 16hrs a day. Not only would they learn something that they are interested in but, all learn to learn - and be better in all subjects.
In Toronto some kids that are on verge of dropping out are transferred to a special school that focuses on skate-board building, and the business around selling skate-boards. http://oasisskateboardfactory.blogspot.com/ Its had some success.