Like you said, the cost varies among countries and families. Homeschooling is hardly a thing here, school books etc are necessary for children 7 years and up here. Uniforms too. Although uniforms can last for years and cheaper overall because the child don’t have to wear normal clothes during most of his/her schooling years. (Singapore’s schools require uniforms)
Education system is also different, public libraries here are absolutely useless when it comes to textbooks etc. I remember going there as a kid and having a hissy fit, lol!
The clothes i use at home are mostly hand me downs from my oldest brother, so you can imagine how girly i must look (Do anyone even buy clothes to wear at home? Waste of money)

But when it comes to clothes to wear outside when hanging out with friends, events, church, and now, school (higher education), it’s pretty hard to find cheap clothes imo.
School allowance for the month for 7-12 year olds can usually add up to 70-100 a month (or less, depending on the child’s schedule).
And then the transport fee for a school bus to come and pick them up. If you choose to send them to and back from school, gas $$ also counts. If the child were to take public transport, it could be 25-30 a month.
If a child wants to take part in clubs or stuff like that, you might have to pay a fee
If a child wants enrichment classes/etc to develop his or her hobbies, and you have no guts to deny them that, that counts too.
When the child is 13+, transport fee is still 25-30 a month, allowance will be more than $150 (school hours can be really long, so the child usually eats at least 2 meals in school) School materials-test papers, books, stuff like that. That really depends on the school though. But I remember spending $100 excluding textbooks on testpapers to prepare for my finals last year
These teenagers probably have handphones, so those bills also count. Shampoo, face cleanser, etc etc also counts.
Then you have to pay for the exams. The government decided that our finals should be free last year, but it was a one time thing I believe.
Then comes tertiary education. If a child decided to take A levels, school fees can be quite cheap. If the child decided to take a diploma, it’s 2k a year. Add in allowance, which will be 250 and above because the price of food is higher in these schools. Also cost of clothes and shoes. I just spent $80 on formal attire (pencil skirt, button down top and really cheap shoes) because we have to do presentations.
The cost of a laptop 1.3k-2k (necessary for those studying in a polyechnic here)
And then university and blah blah.
Can you hear me crying
Oh not to mention medical bills. If your wife has complications with the pregnancy, your child falls seriously sick or was in a car accident, or if your child needs go for therapy or something.
Keep in mind that this is all based from where I’m from. I know it’s also expensive to raise children in other places, but my country is known to be one of the most expensive places to live in. We receive financial help, but we are still struggling to the point where my allowance comes from the scholarships I receive over the years that was meant for my university fees.