How tough could it be? Pick a start date, settle on an end date, throw a few holidays in between and, presto, you have a calendar for the next school year.

But the people who do the picking and the settling and the throwing say their task is far more complicated and controversial than it appears, and the nation's growing religious and cultural diversity makes it harder than ever.

"I still have the bruises," said Patti Caplan, director of public information for Howard County schools, with a laugh. She led the process of creating the district's 2003-04 calendar, which goes to the Board of Education for approval next month.

"It is very tough," said Dan Jackson, who was in charge of plotting out the school calendar for Fairfax County. "We get a lot of people who are not pleased with what we mark up."

There are, in fact, folks who gripe about virtually every one of the many decisions that go into a calendar, educators say.

Deciding whether to start before or after Labor Day is a hot issue, as evidenced this month when many Montgomery County parents protested the school board's approval of a pre-Labor Day start for next year. The end date isn't a cakewalk, either: There is summer school to consider, and the fact that many high school students compete for summer jobs with college students whose classes end in May.

Holidays may be sheer delight to celebrate, but they are a pain to plan. Some parents want short winter and spring breaks for child-care purposes; others want long breaks, including parents whose homelands are on other continents and lobby for extra time to travel there for holidays.

There are issues around teacher development days: how many, when and whether they should be half or whole days.

There's the delicate positioning of teacher work days and teacher-parent conference days. Ensuring enough instructional time before testing is key, too. Toss in the issue of bad-weather days -- some districts build a few in, others extend the school year as needed or cut back on spring break -- and the job turns out to be a bear.

"You have a number of yin and yang influences on the calendar," said Brian Porter, spokesman for Montgomery County schools. "But a lot of these considerations get lost when the calendar gets boiled down to a magnetic plate for the refrigerator or a Post-it note for mom or dad's datebook."

School districts spend many months sorting out the next year's calendar, often starting a year or more in advance. That is not only because it takes time to sort out the myriad details, but also because parents insist on plenty of leeway to help them juggle complicated family lives -- from deadlines for summer camp registration to national park reservations.

An exception is the District, which won't consider next year's calendar for several more months because it has always been done in the spring, said Ralph Neal, assistant superintendent for student services.

In most districts, committees with representatives from various constituencies, including parents, teachers and administrators, are appointed by school superintendents and meet periodically to thrash out the issues.

They start with the givens, such as the number of days students must be in school. Virtually all school systems require at least 180 school days, but some build in more; Fairfax has 183 days set for next school year and Montgomery 184.

Calendar committees must also meet state holiday mandates -- the District closes schools for every federal holiday, while states pick and choose -- and address instructional needs in an era of high-stakes standardized tests and changing curriculum.

The testing factor is what's largely driving the movement toward August start dates, as school officials try to cram in more learning days before state exams. Some states, such as Texas, have mandated pre-Labor Day start dates, which has spawned an opposition group called Texans for a Traditional School Year. The critics argue that it negatively affects an area's economy and hurts families.

Virginia school systems seem to have the opposite problem. The state legislature has mandated a post-Labor Day opening, but some school systems don't like that, either.

"What really crimps our style and ability to do things is the mandate that we can't begin school until after Labor Day," said Jackson, director of the Office of Equity and Compliance in the Fairfax district. "The School Board pleads every year with the legislature to change that, and it falls on deaf ears. It is euphemistically referred to as the 'King's Dominion bill.' . . . The sooner kids go back to school, you don't have a lot of traffic in the [state] parks."

This month, scores of Montgomery parents bombarded school officials with e-mail and letters over the decision to start school next year on Tuesday, Aug. 26, when students have off the following Monday for Labor Day.

Beth Martin, a leader in the Eastern Middle School Parent Teacher Student Association, said parents "didn't feel like four instructional days would have a huge impact on standardized testing" but would crimp vacation plans.

The standard school week is five days, though more than 100 rural districts across the country have switched to four school days a week -- with longer hours -- to save money. For some, that has helped teacher and student morale, while others complain that the long days are exhausting. School districts in a few states are experimenting with year-round schooling.

Calendar designers have other issues to consider, such as days when so many students and teachers traditionally don't show up that opening seems silly.

In Bland County, Va., the opening of hunting season is an event, and schools closed for it Nov. 18. In neighboring Wythe County, the schools stayed open, but it was hardly a normal day; at Rural Retreat High School, 164 of the 365 students were absent, most related to hunting.

Many districts close for Election Day, and Fairfax even closes schools for presidential Inauguration Day every four years, said schools spokesman Paul Regnier. "So many kids were kept out, Democrats some years, Republicans some years," that it became too much of a hassle, he said.

Controversy arises when religious holidays are involved. Schools are not constitutionally allowed to close to accommodate a religious need, but there are practical secular reasons for shutting on a holiday, said legal scholar Charles Haynes of the Freedom Forum's First Amendment Center. Simply, he said, there may be so many absences that a school questions the value of holding classes.

In Dearborn, Mich., where Arab Americans are 20 percent of the population and more than 40 percent of students enrolled in public schools, schools were closed Dec. 5 and 6, the end of the Islamic holy month of Ramadan, during which celebrations are held. And Howard and Montgomery county public schools, among others, close on a few Jewish holidays.

Increasingly, members of other religious groups, such as Bahais, Hindus and Sikhs, ask school systems for recognition of their holidays, as they believe Christians and Jews are being accommodated for religious reasons.

"It is a constant source of tension in a lot of school districts, especially as we grow more and more religiously diverse," Haynes said. "The calendar sometimes can be a flash point for people who are angry because they feel they are left out or ignored."