There are several tests of life and functional skills. Rather than reading and writing, these skills are more like eating and talking. The best known is the ABLLS (pronounced A-bels) or Assessment of Basic Language and Learning Skills. Designed as an instrument for assessing students specifically for Applied Behavioral Analysis and discrete trial training, it is an observational instrument that can be completed through interview, indirect observation or direct observation. You can purchase a kit with many of the items required for certain items, such as "naming 3 of 4 letters on letter cards." A time consuming instrument, it is also meant to be cumulative, so a test book goes with a child from year to year as they acquire skills.
Another well known and reputable assessment is the Vineland Adaptive Behavior Scales, Second Edition. The Vineland is normed against a large population across ages. It's weakness is that it is comprised of parents' and teachers' surveys. These are indirect observations, which are really susceptible to subjective judgement (Mommy's little boy can do no wrong.) Still, when comparing language, social interaction and function at home with typically developing same aged peers, the Vineland provides the special educator with a view of the student's social, functional and pre-academic needs.
The Callier Asuza Scale was designed to assess the function of blind-deaf students, but is also a good tool for assessing the function of children with multiple handicaps, or children on the Autistic Spectrum with lower function. The G Scale is the best for this cohort, and is easy to use based on a teacher's observation of a child's function. A much quicker tool than the ABBLs or Vineland, it provides a quick snapshot of a child's function, but doesn't provide as much descriptive or diagnostic information.