People tell me this fairly often. I'm glad if they think this, because most weeks, I disagree. But if it's someone my age saying it, it's usually followed by, "That's why we don't come very often. Ours just won't behave." I want to ask them why they think my kids are good in church. Could it be because I take them, without fail, at least twice every week (once on Sunday, once to the Wednesday night Low Mass which is of course shorter, but without any of those helpful musical breaks to drown out some shouting)? Furthermore, it takes some effort to get them to be good. Most days my "Thanks be to God" is in reference to the wrestling match ending almost as much as it is for all that salvific business. It is tiring to keep a very little person happy enough to be quiet for an hour, and trying at the same time to make it really be church for the older ones (helping them sing, say the Creed, fold their hands, etc.).
Our church doesn't have a nursery, and I don't miss it. I've never understood the parents who perfunctorily bring in their two-year-old for the first 10 minutes and then reward the kid's screaming by taking him to a room full of toys. When we were at a church that had a nursery, I had to leave a lot, but I stood with the offender(s) in the narthex and kept enforcing quietness and church-appropriate behavior. Perhaps this is another reason my kids at least know what's expected of them at church, even if the little sinners can't pull it off all the time. We also sing the liturgical canticles and (if we have our act together enough) the hymn of the day for the upcoming Sunday at bedtime. Yes, my kids are better in church than a lot of kids their age, and it takes work.
Incidentally, this is one thing the big family papists don't get. They've always got a nice pious dad to share the weight on Sunday mornings. My kids' nice pious dad is always delivering a nice pious sermon, so I count on God to provide me with some other nice pious person to help me with the wrangling (which, thankfully, almost always happens on Sunday). Getting a houseful of kids and oneself ready for church with no assistance is a real chore, and then you have act like you're not already completely exhausted at 9 am, and get through the standing and the singing and the shushing. I guess I can't think of a better time to receive the Blessed Sacrament.