Look at Scheidt v. Tri-Creek - it may help with your questions
LegalSchmegal,
I am not assuming that your request for absence would be for time between Rosh Hashanah/Feast of Trumpets and Yom Kippur/Day of Atonement. I'm going to guess that the reason you need ten days is for observance of Sukkoth/Feast of Tabernacles (allowing for a little travel time to and from). If that is the situation, there is a case that might help you. The case is Scheidt v. Tri-Creek. The summary is available on the US DOJ site at
Educational Opportunities Section Case Summaries
I don't know if the same would apply to your case since this is a primary school case and you are in secondary education. The full brief is available through a link in the second paragraph. This case was settled in favor of Ms. Scheidt and the policy was changed accordingly (search for Tri-Creek BOE and their current policy). The brief also references a previous federal court decision of a similar nature from the 1980's that dealt with the same issue.
I've included the summary of Scheidt v. Tri-Creek from the DOJ site here (it is listed as under the Elementary and Secondary category so maybe it would apply):
Scheidt v. Tri- Creek School Corporation
Elementary and Secondary Education Religion
The Tri-Creek Corporation School District in Indiana had an attendance policy that allowed for only one day of excused absences for religious observance. After a student missed more than one day for religious worship, the District’s attendance policy stated that the student would be given an unexcused absence and subjected to various sanctions, including loss of academic credit, inability to make up work, and suspension. The policy also stated that legal action may be taken against the parent.
After receiving a complaint about the enforcement of Tri-Creek’s policy, the United States intervened in the case, Scheidt v. Tri-Creek School Corporation, on behalf of Ruth Scheidt and her son, M.S., both adherents to the religious tenets of the United Church of God. During the 2004-05 school year, M.S. was given eight unexcused absences for documented religious attendance; teachers failed to allow him to make up classwork; and the district threatened expulsion and legal action, including the filing of educational neglect charges against Ms. Scheidt. On August 10, 2005, the Section filed a brief asserting that Tri-Creek’s attendance policy violated Ms. Scheidt and her son’s right to exercise their religion freely, and Ms. Scheidt’s right to raise her son consistent with her religious beliefs.
Shortly after the Section's intervention, the District and the plaintiffs reached a settlement that: (1) absences for religious observances will be recorded as “excused” and credit given for timely make-up work; and (2) school attendance policies will be revised to accommodate religious observances. Unlike in the past, there is now no limit on the number of excused absences a student may receive for religious observance.