Around the US, 180 days of school seems to be the most common standard.
Most schools in New England get two weeks off in the spring semester--one week in February and one week in April, instead of the one week in March that many other areas get.
Some schools in Maine still close for a week or two in the fall, around the end of September or beginning of October, to allow students to work in the potato harvest.
Snow days are also an issue in snow country. Most school districts will allow for school closures on their calendar--there will be 3 or 4 days at the end of the school year that will be used to make up days where the school had to be closed because there was too much snow for the students and staff to safely get to school. If the winter is mild and no/few snow days are needed, those days won't be used.
My sister works at a private Catholic school. When they have snow days, the teachers post assignments on-line and the students are expected to do them at home and turn them in the next day school is open. This way, the school can close for snow days, but still end the school year on time.
Religious holidays vary by school district. Some will only have Christmas off. Others will take into consideration the population that they serve and there might be a variety of religious holidays where the school will close--Rosh Hashanah, Good Friday, Eid Al-Adha.
In New Hampshire, cities and towns have a property tax to fund the schools. However, in some more rural areas, there simply isn't enough money/tax base to pay teachers and keep the schools in good repair. So since the 1990s, there has been some sort of state funding for such areas, to make sure that there is a certain minimum dollar amount per pupil, so that schools won't lose their accreditation.