Have just looked at a handout from our school with the national 'expectation' levels.
They range from 1C to 5, with c being the lowest in each category and a being the highest.
for a year 4 child in our school the expected level is 4C (schools vary as some are disadvantaged, ours is in an affluent area with all children speaking English as a first language - in disadvantaged areas the expectation would be lower.)