I used to attend Holy Family and now St Mary 
A few years ago, when I was still attending Holy Fam, they used to
have very dynamic youth groups that are very active. Sorry, not
able to give you much info, cuz I lost touch with Holy Fam and the
website is not even updated 
For a start, you may want to take part in this activity to get to
know other youth:
YOUTH COUNCIL
Looking for adventure this school holidays?
Join us for Night Cycle 2007: The Food Trail as we discover some of
the best eats along the central east of Singapore! Age: 15 and
above. Date: 7th September, Friday. Time: 8.30pm Starting Point:
Church of the Holy Family carpark. Cost: $2 (if you have your own
bike) or $10 (if you need to rent a bike) Contact Alex at 97531970
for more information.