https://www.investopedia.com/terms/c/cashaccounting.asp
This looks at current costs. The school is a cost every year, so every year that cost shows up on the budget. The problem is that road/water/sewer maintenance often doesn't show up on these budgets because these systems are usually built all at once. Because of this they usually also need to be replaced all at once. To see those costs before they happen, you need to use accrual accounting:
https://www.investopedia.com/terms/a/accrualaccounting.asp
The entire message from Strong Towns is exactly that because cities often use cash accounting instead of accrual accounting in their budgetary processes these lingering issues of deferred maintenance don't show up until they do, and when they do, those costs will simply be too large for the city to cover without very politically unpopular interventions.
Strong Towns makes good arguments about certain things and are critical in a reasonable way of how civil engineering organizations rate the need for more civil engineering works. But the budget discussion makes zero sense.
The biggest expenses for county, city, town, village government are: schools, police & fire, Medicaid share in states that do that, and employee retirement and health. A small/midsize city spends 60% of its budget on police.
Capital projects are capitalized with bonds. Governments have the lowest bond expenses due to tax exemptions. Roadwork is not done in a cash basis. It’s bonded for 10-30 years depending on the job.
LA currently has about a billion dollars of outstanding general obligation bonds (edit: but that does not include all their future liabilities). They're still rated AA, but I presume that is because the credit writing agencies understand how many untapped revenue streams LA has, but again, those will require unpalatable political change. You can’t keep refinancing forever.
Philadelphia, Miami, and Chicago are getting close to junk bond status, and when that happens, the option to refinance starts evaporating very quickly.
My point is that much of what the city can tax has little to do with the city's GDP. Either the landscape of the city will have to change or the current taxation paradigm will have to change.
Again, putting $1B in some perspective, the LA Unified School District budget (which is county-level, so not directly comparable to the city, but anyway) is just under $19B. Maybe someone else can ballpark how much of that is associated to the city. Or look the other things that scale with population: police, medical, waste, social programs, etc.
LA is fine.
The city has a billion dollar deficit right now. Trivial for residents to afford ($83 per person), but difficult to actually implement politically.
If we cut the school budget only when we need to repave roads, we are playing fast and loose with our children’s future. When we set our budgets to be sustainable, we don’t rug pull parents who are trying to build a life in our cities.
Like I'm happy that my (suburban) city requires new developments to connect to a city-wide bike trail network. That's great. I just don't think Strong Towns/Not Just Bikes presents a realistic mental model of the world. They seem to clearly be pushing for a specific vision regardless of facts.