Differentiated Instructions

In our school district, and maybe many other school districts, focus is on "differentiated instruction." I believe students have different modes of learning, and perform at different levels, hence, different strategies should be used to maximize their potential. Students should not only be taught, based on their ability, but they should be tested based on their ability. What about those students who do not have IEPs , are given differentiated instruction during the school year, but have to take the regular state tests? This is a problem, and I think it needs to be addressed locally as well as at the state level.