Boston will offer summer educational opportunities to nearly 12,000 children this year, Mayor Martin J. Walsh announced Thursday, more than doubling the number of students served in 2015.

“The research is clear: Kids who don’t learn over the summer fall behind in school,’’ Walsh said at Berklee College of Music, where city and School Department officials gathered with leaders from some of the summer programs. “That’s why these programs are a top priority, not just of mine, but of everyone in this room.’’

Walsh said the rapid growth “shattered’’ his goal, set in July, of expanding the number of children served to 10,000 by 2017. The city, which had 79 programs in place last summer, will now work with 120.

Students will be learning not only in traditional classrooms, Walsh said, but through experiences in workplaces, the Boston Harbor Islands, the Blue Hills, and at Berklee’s City Music Boston program, a music education initiative for fourth- through 12th-graders.

Schools Superintendent Tommy Chang said summer gives students opportunities to pursue personal interests and develop curiosity. The city’s summer programs, he said, integrate academic study with experiences that enrich learning.

Chang said research shows that the “summer slide’’ — learning lost when students spend months out of school — accounts for two-thirds of the achievement gap between ninth-grade students from low-income families and those from wealthier families.

“When it comes to student success, what happens outside school is arguably just as important as what happens inside school,’’ Chang said. “And learning should occur anytime, anywhere.’’

Chris Smith, executive director of Boston After School & Beyond, a central partner in the city’s summer programs, said children born into poverty, on average, spend 6,000 fewer hours learning in preschool, after-school programs, and summer programs than middle-class children.

The city’s program, called the Boston Summer Learning Community, seeks to address that imbalance.

“It is summer learning, but it gives kids an advantage in the school year in academics,’’ Smith said. “It’s summer learning, but it also equips kids with skills to succeed in college and the workforce.’’

Jeremy C. Fox can be reached at jeremy.fox@globe.com.