i don't know what schools or other parents necessarily consider average, but with my own kids they are reading fluently by age 8. i start to teach reading when they are kindergarten age (about 5 1/2). we start with letter sounds, then digraphs, & build up to sounding out words and then decoding sentences. but i don't consider them actual "readers" until they are fairly fluent (reading actual books well with comprehension - not leveled readers or beginner chapter books).
this has been achieved by age 8 here (well, my son was actually by age 7 - he has read phenomenally well for quite some time & he just turned 9). if it happens earlier or later for other kids, i imagine that's totally normal. even in public school, kids are all over the place with reading in elementary K-3.
Edited by elizawill - 3/24/13 at 8:56pm