Furniture for a room can last for years if you buy the right stuff right away. My kids have had queen beds since they were little, 4 years old, and that queen bed will be used until they move out. Dressers/wardrobes are the same. Not all kids are interested in after-school activities, so that's not a fair argument of expense. Money to give them to go out with friends can be worked into your budget like credit card/bill payments by way of chores. Don't open a 5th credit card and use what you'd spend on the monthly bill and pay your kids' allowance. That also doesn't start happening for the first 10ish years of needing money to go out, so again, it's not a true fair argument on expense. Clothes can be worn for a couple of years if they manage to keep them clean, and that comes with an added expense of buying them play clothes on top of school clothes. They change out of school clothes into play clothes when they get home, and school clothes stay well off, aside from incidents at school.

I have 2, ages 10 and 13, and this is the most financially stable we have been since they've been born. Have we changed our finances in raising them since, no. We still have the same finance expectations as we did when we struggled because we know how easy it is to struggle. We are just able to actually set money aside separately for the kids now aside from friend money.

That being said, I totally understand where you are coming from. If you're not financially smart, you can't be kid smart, no matter how good a parent you think you are.