Whatever the defects of pre-Vatican-II Catholic schools, they were clear about one thing: they were Catholic. They existed because the Church wisely insisted that it was vital for children to be taught the Faith every day, along with reading and arithmetic and the other common subjects. Central to the program was the proposition that there was a distinctively Catholic way of looking at everything, that the Faith informed every part of life.
Math? We heard about the beauty of the order that God had placed in the universe, which math could reveal. Reading? Our textbooks were peppered with little examples of Catholics being Catholic. Geography? We read about the experiences of a family of Catholic missionary teachers in China in the early 1930's. Catholic parents were instructed that it was part of their duty to send their children to Catholic schools unless serious reasons prevented it, because the Catholic viewpoint was different from that of the culture around them.
And Catholic schools couldn't be built fast enough to meet the demand in my little suburban area near Los Angeles. My elementary school classrooms never had fewer than 45 students in them, some years as many as 55. Yet many Catholic kids had to be turned away because no more could be squeezed in.
Fast-forward forty years, and St. Mary's School in Fullerton had to be closed due to low enrollment. In most urban areas, Catholic schools are disappearing fast. Why? Though there have been many intertwined causes, the most important, in my opinion, is that they gradually lost almost everything distinctively Catholic about the education they offered.
If Catholic schools had continued to emphasize the most important thing, the Faith, they would have retained their unique value in parents' eyes. Instead, they gave up on their "brand", accepted the secular model, and touted their better test scores. More and more students in Catholic schools were non-Catholic, so pressure grew to downplay the religious content of each day, relegating the Faith to its own "Religion" class. But now that well-funded charter schools are catching up on that measure, Catholic schools appear to have little left to offer. As indeed they do.
Carrying the Faith forward to the next generation will always be a winning proposition for Catholic schools. But live by the test score, die by the test score.