LYNN – Supporting one of their own and helping to raise money for a good cause, the Lynn Public Schools Jazz Band volunteered its time at the annual Arthritis Foundation Walk in Beverly Sunday afternoon.Lynn Classical High School junior Cara Garrity has been in the city’s music program since the fourth grade, about the same time that she was diagnosed with arthritis. Two years later, Cara and her mother, Barbara, a special education teacher in the Lynn Public Schools, joined the Arthritis Foundation to help support research of the disease.Dealing with her condition has not always been easy for Garrity, who had two knee surgeries in 2007 and 2008 and a bone cut out of each leg in order to strengthen them and improve her walking.With support from her doctors and the Arthritis Foundation, Garrity was able to make it through the surgeries and is now the drum major in the LPS marching band, a flutist in the orchestra and concert band and a pianist in the jazz band.As a way of giving back to the foundation, Garrity approached her friends in the jazz band and asked them if they would provide some entertainment at this year’s walk, held in Beverly’s Lynch Park.The band obliged, as everyone turned out to play a free concert for the foundation supporters and special guest Red Sox mascot Wally the Green Monster.The concert helped to contribute thousands of dollars that were donated to the charity.”This is a good display of support to fellow students,” said Fine Arts Director Joe Picano. “It is proof of the many things that we teach in the Lynn school system. These particular students do so many things for the community, in and out of Lynn.””They are definitely goodwill ambassadors who represent our city,” added Mayor Edward J. Clancy Jr.Garrity and the jazz band will join the middle and high school bands, concert band and orchestra for a concert tonight at Breed Middle School. The all-city event will begin at 7 p.m.