ARLINGTON, Va. -- Some school officials in northern Virginia said they are worried that undocumented immigrants will not respond to a census that helps determine funding for local school systems.

A new public service announcement in Spanish urges Virginia parents to take part in the state's census, which takes place every three years.

With illegal immigration such a hot topic and tough immigration policies taking effect in Prince William County, some officials said they are worried undocumented parents won't respond.

"People are afraid, and any mail that they receive at their homes, they double-check what it is," said Ernesto Campos, who reaches out to the Hispanic community for Arlington County schools.

The census cards, which are just being mailed out, don't ask for last names, just the first name and age of anyone in the household under age 19.

The census ad campaign aims, in part, to let undocumented immigrants know information is confidential and will not be passed along to law enforcement.

"That is our concern, that people, because of what is going on in other jurisdictions, that people will feel we're trying to gather information for some other purpose," said Robert Smith, Arlington County Schools superintendent. "This is our only purpose, and Arlington is taking a stand, as some other communities, that we want to be a welcoming place."

U.S. Rep. Jim Moran joined local Virginia school officials at a news conference Friday afternoon in Arlington. He said he is worried that schools will lose out if parents do not respond to the survey.

School funding from the state depends on the census. In Arlington, each student listed on a census card means about $2,300 to the child's school system.

Virginia schools are prohibited by law from asking about the immigration status of any student.

Prince William County school officials said they chose not to take part in Friday's news conference because they take a more low-key approach to the census.