Prior knowledge (or schema) is basically what your child knows. As Debbie Miller from Reading With Meaning puts it, “[Prior knowledge] is all the stuff that’s already inside your head, like places you’ve been, things you’ve done, books you’ve read—all the experiences you’ve had that make up who you are and what you know and believe to be true.”
The reason it is so important is that a child’s prior knowledge directly affects how well she comprehends texts. It is very difficult, even for adults, to pick up a book for which we have little to no background knowledge and comprehend it. All you have to do is hand me a manual to install a light switch and I go brain dead! Lucy Calkins reiterates in her book, The Art of Teaching Reading (pg. 444), that “one of the biggest problems readers encounter when they read…is the need for background knowledge.” Young readers need our support to comprehend texts by building up their schema.
Helping your child gain prior knowledge isn’t hard. As a matter of fact, you probably do it every day without even realizing it. It can include things like taking a trip to the beach, reading a book about trains (for the 100th time!!), watching a DVD about volcanoes, going on a field trip, or talking about word meanings and expressions.