I can't understand how people think that having two children close together has a similar financial impact as having twins (or higher multiples) .
As a mum of dearly loved DTs, this makes me annoyed because parents of twins have to buy two lots of baby equipment (double pram, two cots, highchairs, nappies!!) at the same time and as they grow nothing can be passed down. Also have to pay two lots of childcare/nursery fees, when they want to do activities they can only do them if you can afford to pay twice (mine have to do exactly the same things as I'm not having either of them miss out). When they start school, two lots of uniform, coats, shoes not to mention trips, then there's beds, larger car, university fees etc, etc.
At least parents who have kids close together can reuse a lot of stuff and anyway, it is their CHOICE to have them close together, you have no choice over whether you have twins and I don't believe that anyone who decides to get pregnant thinks 'oh, better wait until I'm sure I can afford 2 in case I have twins'. People who have children close together can plan to space out their children if they can't afford it.
Therefore, I think schools should help out parents of twins, triplets etc and they should not have to pay the same as singletons!!