What's involved in "retro-fitting"? I don't imagine a room designated as available for praying requires much in the way of infrastructure. Do the Catholic kids need somewhere to pray regularly?

Do you have the same objection to schools providing space for extra-curricular clubs that cater to only a handful of students? How about sports teams that only have 24 kids on them? Should the school really be devoting resources to something that only a few kids participate in?

Your arguments are thin, to say the least.