I started school at age 5.
My mum bought me a Ladybird book just before I started school, and read it with me. That was my
introduction to actually learning to read for myself.
During that first term at school, I remember going back into the classroom after playtime, and the teacher had written lots of similar words on the board to practise with us: the, they, then, them etc. As I can still picture that board in my mind, I am fairly sure that I could read them all perfectly well by then, and when I moved to a different school after one year, I could certainly read simple books very easily.
I could write too - every Monday, we had to write what we had done over the weekend. It's funny what you remember, isn't it - I remember having to ask the teacher how to spell missis (Mrs). She said the letters m, r and s, to me, but I didn't see how that could possibly be right (but was far too shy to say anything), so made up my own phonetic version instead 
One of my sons learned to read very quickly after starting school, and has always loved reading.
His brother still couldn't read after a year at school, so I taught him using flashcards over the summer holidays, as I could see that he would soon get behind in other ways if I didn't, after noticing at the parent's evening that the maths cards that they worked from required reading skills too!
Unlike the rest of our family, that son has never enjoyed reading fiction, but soon put his newly-acquired reading skills to use with non-fiction.
One of my grandchildren did not find learning to read easy, despite having always loved having books read to him, but he got there at his own pace and is an avid reader now (age 9) and his literacy skills are well above average.
His younger sister (now 8) learned to read more easily, but still doesn't enjoy reading to herself at all.
All children are different!