Catholics not getting involved in the world is a different matter than sending one's impressionable children (who don't have Catholic or any other kind of values yet!) to the proverbial slaughter.
Public schools are houses of indoctrination into the liberal (increasingly leftist) insanity of the modern world. Do you want your children to be taught that sodomy is OK? Do you want your children to realize they are transsɛҳuąƖ, thanks to the constant barrage of propaganda they receive at school? Do you want your girls to lose any feminine modesty (from being around immodestly dressed girls all day, and peer pressured into thinking THAT is normal and Mom & Dad are "weird")? Or for that matter, your girls will lose ANY femininity, since schools are completely feminist. Your kids will learn about White Guilt, the patriarchy, the oft-disproven myth of the "wage gap" but taught as fact, they will learn that masculinity is toxic, they will be taught Evolution, that the world is overpopulated and birth control is a virtue, they will receive co-ed, graphic Sex Education... -- I could go on for hours.
And let's not even start on Common Core! The whole point of public school is to give your children an education, right? Well then you better not send them to public school for that reason alone. Common Core is DESIGNED to create idiots who will go along with whatever their masters want. But even before Common Core, the type of education received at a Public School was NOT designed to create strong Catholics, ready to be leaders.
Anyone reading this who received their public school experience 15 or more years ago is NOT qualified to speak from a standpoint of Experience about Public Schools today, in 2018.
I went to public school myself. I graduated in 1995. But guess what? This isn't the 80s or the 90s anymore. When I was a kid, calling someone "gαy" was the ultimate insult. And there were only 2 sexes. Today, calling someone "gαy" would be a hate crime, a word that many consider actually harmful (as in, inflicting harm) upon another. Sticks and stones, what's that? You didn't have a sodomite character in every movie and TV show until sometime in the mid 2000's. And SJWs were just a "worst nightmare" for a few people with very vivid imaginations back in the 80's. And we didn't have cell phones or social media back then.
While it's true that older teens and young adults need to go out into the hostile modern world, well trained for battle, that doesn't mean that you should send your 5 year olds into the battlefield! That's ridiculous.
Before a certain age (the fine details of which are open for debate) -- let's say 12 years old at least -- near-complete sheltering is the only answer. No unsupervised Internet, no phone, constant supervision, vetting each and every friend they encounter, previewing anything they read or watch, etc.
Either you care about your childrens' souls or you don't. A young child is a clean slate. That is why it's worth giving up all kinds of Middle-Class luxuries to have my wife stay home and raise my children, rather than delegating that privilege to the State or local daycare.
Matthew