Seattle Prep, run by the Jesuit order, has also asked students, alumni and parents to write letters to U.S. Sen. Maria Cantwell, D-Wash., Secretary of State Hillary Clinton and other officials in support of Knox, Seattlepi.com reported.
Knox, who graduated from Seattle Prep in 2005, was convicted in December in Perugia, Italy, of killing British student Meredith Kercher. The young women were sharing a house while spending a year studying in Italy.
"Whenever we have prayers for Amanda, we always have prayers for Meredith and her family," said Kent Hickey, the school's president. "We want to support Amanda and her family, but we always recognize the Kercher family is in need of great support. We're also writing letters of support to their family."
Buyers of tickets to a Tuesday night basketball game were to be asked if they wanted to make contributions to Knox, who is appealing her conviction.
Knox was sentenced to 26 years in prison and her former boyfriend, Raffaele Sollecito, to 25. A third defendant, Rudy Guede, who was convicted in a separate trial, had his sentence reduced to 16 years on appeal. Lawyers for Knox and Sollecito argued that Guede was the only killer.