A kid programming an iPhone app could be programming at a high level and doing neat stuff, but you clearly indicated that he is doing plain vanilla programming,

A kid programming an iPhone app could be programming at a high level and doing neat stuff, but you clearly indicated that he is doing plain vanilla programming, so I'm going with the Algebra level. That's not to say your son isn't advanced (making any kind of working app is far above the level of most 11 y/os), just that the actual math probably isn't complicated, it's the concentration and attention to detail and creativity and being able to work with APIs that he's really getting ahead in. I'll concede the point that certain projects require math skills in certain areas, and CompSci PhDs need to understand some obscure parts of the math world (lvl 20 if Calculus rates a 10), but making an icon move around a screen is more like writing a recipe on how to bake a cake than it is mathematics.