PHILADELPHIA — On the eve of a board of trustees meeting called to consider changes to the Greek system at Pennsylvania State University, the parents of deceased fraternity pledge Tim Piazza have called for the expulsion of the students and the firing of the employees responsible for their son’s death.

“It is time for Penn State to take the lead,” James and Evelyn Piazza wrote in a four-page letter to the board. “The whole country is watching.”

The Piazzas urged the board to set new guidelines that would call for all students found guilty of hazing or failing to report it or furnishing alcohol to minors at Greek socials to be subject to expulsion. They also asked university officials to stand with them in fighting for tougher laws against hazing, and they demanded that the university accept responsibility for their son’s death.

“Our son died on your watch because of ignorance and denial by Penn State,” the Lebanon, N.J., couple, both accountants, wrote. “It’s time to admit responsibility so that the university can move forward.”

Penn State did not immediately respond to a request for comment.

In response to the letter, Penn State issued a statement that read: “Our focus is on solutions to the problems of student alcohol misuse, hazing and other misconduct. Tomorrow (Friday), at 1 p.m. during the public session, the university will discuss our plans to advance student safety.”

Piazza, a 19-year-old sophomore engineering major, was forced to drink large amounts of alcohol and later fell down some stairs during a Beta Theta Pi pledge night party in February, according to the grand jury presentment that indicted 18 fraternity members in his death on charges ranging from involuntary manslaughter to aggravated assault and hazing. No one called for emergency help until about 12 hours after he was injured during the fall down the stairs. In the interim, Piazza was slapped, had liquid poured on him, and fell several other times. Piazza died of a nonrecoverable brain injury, a ruptured spleen and a collapsed lung.

Penn State’s board has permanently banned the fraternity and instituted a moratorium on alcohol at social events last semester, as well as reducing the number and size of allowable parties and banning kegs and hard liquor.

The board is meeting in private today to discuss potential changes.