In Year 4 the numbers children are expected to be able to read and write increase in size, to include 4-digit numbers. The process is the same as with 3-digits above. Children can explore what a thousand is using concrete materials (a 10x10x10 cube) and pictorial representations. The key is that 1,000 is made up of ten hundreds.
The debate about how to write 4-digit numbers has been ongoing. One thing everyone agrees on is that it is important to keep each set of three digits separate, making it much easier to read. Some prefer a space between the thousands and hundreds e.g. 3 456. The latest national curriculum encourages the use of a comma e.g. 3,456. In most of Europe the comma is used to separate whole numbers from decimals, known as a decimal comma, so using a comma could be confusing. Calculators often use an apostrophe e.g. 3’456. What a lot children need to know!