Is school districts allowed to cross counties?

Yes, school districts are allowed to cross county lines in the United States. It's not uncommon, especially in sparsely populated areas or where geographical features make it impractical to confine a district to a single county. The specific rules and regulations governing this are determined at the state level, not the federal level. Each state has its own laws about school district boundaries, and these boundaries are often established based on factors like population density, geographic considerations, and historical precedents.