Desdemona is absolutely right about music directors and music education.
1. Hire a good music director for the parish. A real musician with a Catholic music background. Ours is a treasure. You have to spend the money to get a good man.
The Episcopalians may be a bunch of heretics, but they take their music seriously. In our former ECUSA parish, the vestry asked the music director what he needed for his budget, and then everybody else fought over the rest. I am not kidding - that is exactly how it worked. Until you make music a top priority, it won't improve significantly.
2. Bring back music education in the Catholic schools and in Sunday School. Our parish school is doing this already, with fabulous results. The choirmaster teaches a credit course in Western Church Music to great acclaim -- and the kids get extra credit for singing in one of the choirs.
3. Children's choir. I have already sent our children's choir director all the links and information on the Royal School of Church Music program -- it has ranks and awards for passing various music exams, the kids get medals with different colors of ribbon depending on the level of exam they have passed. There is also a national exam which entitles a kid who passes it to wear a special medal of bronze, silver, or gold. Nothing like a little competition and reward to get the kids going. It sure worked in our former parish!