From this page you can access the National Curriculum content for Year 3. The content for Maths and Science is specific to Year 3. The content for English is prescribed for lower Key Stage 2 (i.e. years 3 and 4), while foundation subjects are prescribed only for the whole of Key Stage 2.
Schools are only legally required to teach the content by the end of the Key Stage, so can change the year group in which a specific objective is taught if they wish.