D.C. School Superintendent Clifford B. Janey ordered all the city's public schools to close early yesterday after some principals reported classroom temperatures approaching 100 degrees, and officials said the heat might force another early dismissal of classes today.

Janey's decision to release students at 12:30 p.m. focused attention on one of the school system's long-standing problems: aging infrastructure that causes many buildings to be too cold in the winter and too warm in the spring. About 100 of the system's 145 schools -- many of them built in the World War II era -- have no central air conditioning, and 20 have faulty air conditioning systems and windows that cannot open, officials said.

There were no heat-related closings yesterday in other Washington area school systems. Baltimore public schools, however, closed 21/2 hours early.

D.C. school officials said Janey ordered an early shutdown of all schools, including those with working air conditioning, to minimize disruption in families with children at more than one school.

But several parents who had to interrupt work to pick up their children or scramble for babysitters questioned the decision.

"It's an absurdity. This is the kind of thing that gives the school system a bad name," Wendy Jacobson said as she arrived to pick up her first-grade son at Oyster Elementary School in Northwest, a four-year-old building that is fully air conditioned.

Philip Mueller came to Oyster to pick up his two children from their first-grade and pre-kindergarten classes. "Half of the people here probably don't have air conditioning at home half as good as it is here," he complained. "They'll bake at home."

School board President Peggy Cooper Cafritz said one reason for the system-wide closing was that the school facilities department could not provide an accurate list of which buildings had functioning air conditioning. Two school administrators denied that, saying that such information was available.

Officials said that students should report to school at the usual time this morning and that Janey will determine by 10 a.m. whether to dismiss classes early again. The weather forecast for today offered no relief, with a high to match yesterday's 92 degrees.

"There will be a combination of things going into the assessment: the weather and air conditioners -- are they working?" said Peter G. Parham, Janey's chief of staff.

Parham said principals were issued new guidelines Monday that called for them to contact the facilities department if temperatures in their buildings reached 90 degrees. In such situations, an inspector is sent to the school to determine whether the air conditioning system is functioning and, if not, whether fans can bring down the temperatures to an acceptable level, he said. Parham said any principal who is not satisfied can request an early dismissal.

Recreation centers were opened early to accommodate students who had nowhere to go yesterday.

At Anacostia Senior High School in Southeast, which has no central air, students trickled out of the building after the early dismissal. The heat appeared to be taking its toll, as some students emerged with their pant legs rolled up high or their sleeves tucked in.

At Martin Luther King Elementary School, also in Southeast, fourth-grade teacher Georgie Wiley led Washington Teachers' Union Vice President Nathan Saunders and a reporter on a tour of her third-floor classroom. She pointed to an air conditioning unit that, she said, hadn't worked in two years.

Two fans were running, but a digital thermometer Saunders brought to the school registered 91 degrees.

"We have some kids with asthma up in here," Wiley said, adding that in recent days she has suffered from several heat-related ailments. "I think [Janey] should come to the school to see how unbearable it is for students to learn and teachers to teach."

Officials in several suburban Washington systems said that virtually all their schools have air conditioning. In Prince George's County, officials said 14 of 196 schools lack air conditioning but will get window units installed over the summer under a $10 million initiative.

The D.C. school board, after years of getting less capital funding than anticipated from the D.C. Council, voted recently to scale back a plan to address infrastructure problems through major rebuilding and modernization of schools, opting instead to allocate more money to short-term repairs.

Thomas M. Brady, the system's chief of business operations, said yesterday that repair crews have been dispatched to fix as many school air conditioning systems as possible before the last day of classes Tuesday and the beginning of summer school July 5.

But he said the air conditioning likely will not be fully operational until late August, when the new school year begins. "Give us a couple months, and I guarantee the air conditioning systems will work," he said.

Staff writers Nick Anderson, Tara Bahrampour, Theola S. Labbe, Robert E. Pierre and Paul Schwartzman contributed to this report.

Carmelle Henson picks up son Rashid Brown Jr., 7, from Martin Luther King Jr. Elementary School in Southeast after early dismissal.Like many parents, Linda Booze said she left work early to pick up her son from King Elementary School, where classroom temperatures reached into the 90s.Students, not all of them disappointed, catch their rides after early dismissal at Martin Luther King Jr. Elementary School.