Contrary to popular belief, most aspies aren't born with amazing reading or mathematics skills. These are reserved for the select few. Most aspies seem to have difficulty at school academically in the early years and socially in the later years.
The Aspie Learning Catch-22
Some of the biggest problems aspies face, particularly in the primary school years, is the ability to concentrate on a topic (motivation). The problem is that the aspie tends to be very focused on his or her special interest and has great difficulty maintaining focus on other things.
In the primary school years particularly, other things cannot become interesting until the aspie overcomes some early hurdles. Reading is a good example of this. While there are undoubtedly a lot of books out there which would satisfy the aspie child's special interest needs, these books aren't accessible until at least rudimentary reading skills are acquired.
It's a Catch-22, the aspie child can't enjoy reading until they already have basic reading skills, but they can't easily develop these skills until they can enjoy reading.
Overcoming the Problem
The crux of the problem is that the aspie has great difficulty developing those rudimentary reading and mathematics skills because they are unable to sustain an interest in their learning materials.
The special interest is absolutely key to learning in Asperger's children and you should use it whenever possible.
This means that parents often need to become writers, rather than simply being readers. If your child comes home with a book, for example; a Dick and Jane book, you may need to rewrite that book to use the names of Transformers, video game characters, Saturday morning cartoon characters or even pets/animals. This rewriting isn't very difficult but will substantially increase your child's chances of learning the work.
Similar liberties need to be taken with speaking and writing and when possible, the child should be encouraged to speak or write about their favorite topics rather than being forced to use school only topics.
Good examples of where this can be achieved include situations where a child is asked to write a sentence with a particular word in it or where they are presenting "News" to the class.
I am not suggesting that the child should be allowed to follow his own particular agenda based entirely around the special interest for the majority of the school year. Schools cover a variety of subjects including history, science and religion which obviously cannot be based around the special interest (unless there is direct relevance).
Often those other subjects will be interesting in their own right and it's normally the basic building blocks - reading, writing, spelling, speaking etc which really benefit from the inclusion of the special interest.