In recognition of Pittsburgh's 250th anniversary and the Pittsburgh Public Schools' efforts to boost academic achievement, the Senator John Heinz History Center is admitting city school groups for free through Dec. 31.

School Superintendent Mark Roosevelt and Andrew Masich, history center president and chief executive officer, will make the announcement at 11 a.m. today at the Strip District museum.

The decision affects about 28,300 students in district schools. Free admission also will be offered to students at city charter schools, which are independent public schools.

"We felt this was the right time to do our part to help the Pittsburgh Public Schools," Mr. Masich said. "Mark Roosevelt and others are working hard to bring the standards of education back up to where we feel they should be."

Region-wide, the history center annually draws about 35,000 students on school-sponsored trips. Mr. Masich wasn't able to say how many of those are Pittsburgh school students but said the number of city-school visitors has been dropping in recent years, perhaps because of the cost.

The history center charges $5 per student. Individual schools and parent groups often pay for field trips because some students otherwise couldn't afford to go.

The district previously arranged for ninth-graders to visit the history center this school year as part of a new civics course. Now, spokeswoman Ebony Pugh said, all 65 schools will be encouraged to arrange visits by Dec. 31.

Mr. Masich said he and his board discussed how to aid the school district's improvement efforts and determined free admission was "what we can afford to do. I wish we could do it for every kid in the region and maybe someday, with the proper underwriting, we'll be able to."