When working with a child with special needs, what we need to understand is that they are likely perceiving the world differently than the people around them (but we certainly all do at times!). Depending on where the area of need is, it may just take a different approach, additional repetitions, or modifications so that they can "access" the information that they are being taught.
In all my years of working with students with special needs, I continually grow and gain insight into the various learning differences that make each student so unique. All students can and should be showing progress when the teaching is done right - having appropriate scaffolding of skills, targeting interventions, and appropriate accommodations.
Kids want to feel successful and will generally work harder when they have experienced what it feels like to have success in a subject. Frustration comes when they feel that they cannot do something that they really want to be able to do. The steps might be smaller, but they will make improvements.