Defining what school actually is matters. I’ll pull a definition from Wikipedia, which likely just copied some academic textbook:
Quincy:
| A school is an educational institution centered on instruction. In modern pedagogical views, it's seen as a community involving all its members: students, teachers, parents, specialists, and staff. Through this instruction, subjects acquire knowledge, skills, abilities, and habits. |
If we used a minimalist definition, it would be enough for kids to just pick up some math logic and basic English literacy. They could then take specialized courses later to get a job and, basically, earn a living.
Luckily, it doesn't work that way. The goal of civilization is captured in that definition above: knowledge, skills, abilities, and habits. It's about building well-rounded people with culture and insight. It's the transfer of vital segments from one generation to the next. Religion is definitely a core pillar of human civilization—and for those who are religious, probably the most important one. The definition clearly states that parents are a key part of the school system; passing down essential life values is also part of education.
The only question is whether religious education should receive public funding. I'd say no in places where interest is low. But even that's debatable given how much political correctness and affirmative action are pushed today. We see massive support for various minority groups constantly, so why should religious minorities be any different? In America, where a huge percentage of people identify as believers and a massive number of kids attend religious classes, that funding should certainly be handled the same way.