I'm Jewish, new to Montgomery County, and have learned so much on this thread! Here below is a brief explanation of the Good Friday/High Holy Day connection. URL at the bottom. Happy Halloween to all who observe!
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Judith M. Koenick, a former public school teacher, filed suit against the Board of Education of Montgomery County, Maryland, challenging the constitutionality of a Maryland statute providing for public school holidays on the Friday before Easter through the Monday following. According to Koenick, this statute's enforcement amounted to an establishment of religion because it singled out a Christian holy day for special treatment in a manner not accorded to the holy days of other religions.
A district court rejected Koenick's arguments and ruled in favor of the Board of Education, finding that the Good Friday school holidays did not constitute an establishment of religion. Koenick appealed to the Fourth Circuit Court of Appeals.
In a majority opinion written by Judge Ervin and joined by Judge Motz and Senior Circuit Judge Butzner, the Fourth Circuit Court of Appeals agreed with the judgment of the district court and affirmed its decision, ruling that there was no impermissible establishment of religion in creating a public holiday at the same time as the Christian holy day of Good Friday.
The most important part of the Court's reasoning was the Board's argument that these schools closings served the secular purpose of saving money and maintaining the school's effectiveness in the face of a high rate of absenteeism on those days - the same reasons that the Board closed schools for the Jewish holidays of Yom Kippur and Rosh Hashanah.
http://atheism.about.com/library/decisions/holydays/bldec_KoenickFelton.htm