Answer
Our school started in 1999 with 34 children.
This photograph was taken in October 2006 from the top of the crane (thanks Lawrence!) on the building site. There were around 380 children enrolled at that time. So, allowing for some children being absent on the day and some teachers sneaking into the photo any guess in the region from 350 to 400 is excellent.
We are expecting to have 480 children enrolled in 2009 when we will have two classes all the way from Junior Infants to 6th Class.