They are not funded by the national government. They are mostly funded by city and county governments, with some money from state governments.

Basically each city or county is mostly responsible for paying for the education of the children within its boundaries.

EDIT: I am slightly off on the percentages. See the comment below.

Low-income districts are particularly troubled because of plunging revenue amid the Covid-19 recession. Districts rely for revenue on local property taxes and state subsidies. Poorer districts, where property tax revenue is low, rely on states for most of their income. With states hit hard by falling income and sales taxes, aid to school districts is dwindling in many places. -- TFA

Property tax revenues will also probably be dropping.

They are funded at the state/city level, mainly by property taxes. This is why there is such a drastic difference in quality of education from school to school, and why local school rankings are a big factor in determining housing prices across the country.

They are, but at a hyper local level. School districts generally coincide loosely with city boundaries, and are usually funded through a combination of local taxes (usually property taxes, but it depends on the district), state education budgets, and a small amount of federal funding.

Because the bulk of the funding comes from local sources, when a local economy collapses the school district has no backstop, and their funding can get much closer to just the state and federal funds. When states reduce budgets due to those same economic issues, those areas get devastated.

They are funded by real estate taxes (high housing prices help fill local budgets) and income taxes.

They are, by state and local governments.