The Centre Jean XXIII is a couple of hundred metres from Kirchberg, behind the Philharmonie — but is hidden away in the woods. Because of the numbers involved in our various community events (primarily catechetical: Marriage Preparation, Confirmation classes, First Holy Communion classes) the Centre Jean XXIII offers spacious, suitable facilities, with good parking. If you know the School St Sophie on the rue Jules Wilhelm, then you will find the Centre (also called the Grand Seminaire) 100 metres down the hill, on the same side of the road.
There is a long driveway through the trees — continue to the very top where the car-parks are located to the left and the right.
If you are dropping off one of your offspring for a class, there is a reception area where you are welcome to wait (with vending machines for hot & cold drinks).
For directions follow the Centre Jean XXIII link above, or see the official site.
[update: rue du Fort Thungen (between Melia hotel and rue Jules Wilhelm) is closed due to roadworks at time of posting; access from Kirchberg/Ave. JFK possible via Rue des Coquelicots/rue des Muguets]
This is as clear as I can make it! Good luck!