My DS reached PM level 30 about half way through Yr 1 (age 6 1/2), and moved onto a different system his school uses.
I've read that the PM expected levels are Prep 1-6, Yr 1, 7-12. My son was reading level 26 when he finished Prep, but what I'd say stood out was his speed of progress through the levels. Although he stayed on 30 for a month or two, to let his comprehension catch up with his ability to retain new words he read.
Also worth noting is that the readers nearly killed/prevented his love of reading! They were generally unexciting for him, and not his choice. It took finding just the 'right' series to turn this around, and now he is an avid reader.