By Elizabeth Barber

BOSTON (Reuters) - Convicted Boston bomber Dzhokhar Tsarnaev was once a bright, hardworking child who won the adoration of his teachers and classmates alike, his former instructors testified on Wednesday for defense attorneys trying to spare him the death penalty.

During the sentencing phase of Tsarnaev's trial in federal court in Boston, his lawyers have been trying to paint him as a mostly normal American kid who fell under the spell of his now-deceased older brother, ultimately joining him in the 2013 bombing of the Boston Marathon. It was the worst attack on U.S. soil since Sept. 11 2001.

Wednesday's testimony marked the first time Tsarnaev's lawyers focused testimony on him, instead of the brother, Tamerlan, a boxer turned aspiring jihadi who was died after a shootout with police days after the bombing.

Tracey Gordon, who taught Tsarnaev in fifth and sixth grade at a Cambridge school, described him as an exceptionally intelligent child who easily mastered English after arriving in the United States from Russia and "was eager to learn whatever school had to offer."

"He was a person who you enjoyed being around,” Gordon testified, adding that he would "befriend anybody and help anybody in need."

Jurors were also shown photos of a young Tsarnaev smiling as he learned how to dance, did classroom chores and cradled a teacher’s newborn. At one point a college friend broke down and cried on the stand saying, "I really miss the person that I knew."

The ethnic Chechen, 19 years old at the time of the bombing, was found guilty this month of killing three people and injuring 264 after he and Tamerlan placed homemade bombs at the marathon's crowded finish line.

The blasts killed Martin Richard, 8, Chinese exchange student Lu Lingzi, 23, and restaurant manager Krystle Campbell, 29. The Tsarnaev brothers shot dead Massachusetts Institute of Technology police officer Sean Collier three days later.

Tsarnaev’s attorneys have sketched for jurors how his immigrant family unraveled in the years before the bombings, with his mother and Tamerlan becoming deeply religious.

Prosecutors have painted Dzhokhar Tsarnaev as an equal partner to his brother in the bombing, citing al Qaeda propaganda found on his computer and a note he wrote that cast the attack as retribution for U.S. military campaigns in Muslim lands.

Two college friends tearfully described him as an aspiring marine biologist who was generous and treated women with respect. "He was just there for me," Alexa Guevara, 21, said while sobbing.

(Additional reporting by Richard Valdmanis; Editing by Jeffrey Benkoe and David Gregorio)