kindergarden charges?

Please help?! Just taken my little boy back to kindergarden (playgroup) today after being very ill last week, & i've just been told that i have to pay for him while he's been off! Is this normal? I did ring them to inform them of his absence. Aparently this is also the case when we go on holiday, is this the norm? (he goes 3 mornings per week)
Would appeciate any advice.

Thanks loads!

Elaine