We call it primary school here to and you start at the age of 4. The first year (age 4-5) is reception and then they just go up from yr 1 to yr 6 which is the last year of primary school. The other thing that it might be worth knowing (since I think in Australia the school year runs from January?) is that our school year runs from September to July, but you might already know that of course.
Oh and with the subway thing, yes it is called the underground but I think it is only in London. There are several other cities which have Metros though, (which are basically trams that run above ground), for example Manchester, Sheffield and Newcastle.