Her death generated an outpouring from her former students, some of whom had joined leading ballet companies, including San Francisco Ballet, the Royal Danish Ballet, Houston Ballet, Pennsylvania Ballet and New York City Ballet.

“If we’re lucky, we have one teacher in our lives who makes a difference; someone who teaches us so well in a craft that we learn what we are capable of. More than that craft, we learn a few lessons about life that stay with us always. For me, that was my ballet teacher,” former student Amy Goodman Kass wrote in an online tribute.

Cronsberg was born Jacqueline Ann Kirby in Boston, the eldest daughter of John and Marguerite (Kirk) Kirby. She began her dance studies at the Gertrude Dolan Theatrical Studios near her home in the city’s Roxbury section.

In middle school, she studied with Mieczyslaw Pianowski, a Polish emigre who had danced under Sergei Diaghilev and Anna Pavlova and later spent time in a prison camp after being captured by Germans during World War II.

“My mother told him I was an intermediate dancer. I walked in dressed in shorts, a blouse, and red toe shoes. Everyone else was in correct ballet attire,” Cronsberg told Dance Magazine.

Her academic studies took place at Girls’ Latin Academy and Newman Preparatory School in the Back Bay. After high school, she studied dance at The Boston Conservatory with Jan Veen, who founded the school’s dance program, and ballerina Ruth Ambrose.

In 1966, Cronsberg opened the Ballet Workshop of New England in Sudbury, Massachusetts. As she taught ballet, Cronsberg’s younger daughter, Sandra, pursued dance, studying at the School of American Ballet and later joining New York City Ballet in 1974.

Sandra’s role at NYCB introduced Cronsberg to the company’s founder, George Balanchine, and to the teaching of Stanley Williams, who was considered to be one of the world’s greatest ballet teachers.

“It was an education for me to observe this genius from the sidelines the way I did,” Cronsberg said of Balanchine in a 2004 interview with The Boston Globe.

What Cronsberg learned from Balanchine, she taught her students with vivid instructions, like “heel forward, toe back,” and “turn out your eyebrows.”

Jessica Wilson, another former student, said she incorporated Cronsberg’s phrases into her teaching.

“We have lost someone so dear, but I know she is forever a part of us. I feel immensely grateful to her,” wrote Wilson, now director of dance at the Hopkinton Center for the Arts.

When Cronsberg established the Massachusetts Youth Ballet, she drew upon the breadth of ballet repertory to present excerpts from classics like Swan Lake and Giselle, the works of August Bournonville, Marius Peitpa and Balanchine.

The company performed Balanchine’s ballets staged by Sandra with the permission of The George Balanchine Trust. The performances at the time filled a void for audiences in the Boston area, where Balanchine’s ballets were performed infrequently.

“There are plenty of young dancers of formidable athletic achievement these days. What distinguishes Cronsberg’s crew is their precocity of style: They know what to do with their arms, heads and backs, not just how to execute the steps with their legs and feet. They’ve gotten a kind of total training that is rare,” the Globe wrote in a review of a 2000 performance that included excerpts from Sleeping Beauty and Le Corsaire and two Balanchine works, Valse Fantaisie and Raymonda Variations.

In 2004, the company honored the centennial of Balanchine’s birth with a performance staged by Sandra, coached by former NYCB principal dancer Adam Luders, and included a lecture by the famed ballerina Merrill Ashley.

The Globe editorial board singled out Cronsberg’s company when it marked the anniversary of Balanchine’s birth.

Working behind the scenes was Cronsberg’s husband, Sidney, the school administrator who videotaped performances wearing his trademark red sneakers.

Cronsberg cheered her students from the wings, clasping her hands as if in prayer while young dancers executed challenging steps. She deeply appreciated their successes. The opportunities to perform were few, Cronsberg said, but a flawless showing in a revered ballet endured and provided joyous memories.

Cronsberg found comfort in ballet’s beauty and grace and sometimes watched videos of her company’s performances, which offered the first glimpses of the ballet careers of her students Alexander Pandiscio, Sarah Van Patten, Matthew Neenan and Emily Waters.

Cronsberg traveled to watch her former students perform, and for a time, she lived near the War Memorial Opera House in San Francisco, where Van Patten performs with the San Francisco Ballet as a principal dancer.

Ballet Workshop closed in 2005 and Cronsberg joined the faculty at Boston Ballet School. She and Sidney sold their house in Hopkinton, Massachusetts, and moved to Cape Elizabeth, Maine, where they built their dream home, decorated with family photos, artwork by Erte and posters from the youth ballet’s performances.

In 2016, Cronsberg and Sidney moved to California, where Sandra lives with her husband. Last September, Cronsberg became a great grandmother for the second time with the birth of her great granddaughter, Kayla Isabelle Lahidji.

Cronsberg is also survived by her daughter, Sandra Jean Eshima, and her husband, Shinji Eshima, another great-granddaughter, Theo Claire Gibbons, who was born in 2015, a grandson, Alexander Hurt, his partner, Devon Gibbons, granddaughter, Marguerite Bird, and her partner, Amir Lahidji.

She was predeceased by her husband, who died in 2017, a daughter, Debra Lynne, who died in 1989, and sister, Jeanne Kirby Lindman, who died in 2017.

A memorial service will be held June 6, 2021 at Inn by the Sea in Cape Elizabeth, Maine.