Pharrell Williams’s No. 1 hit “Happy” will be but one of the many largely upbeat songs that will be performed on Sunday by more than 80 young Dorchester and Mattapan vocalists and their greater Boston peers as part of the season’s finale concert by the Boston Children’s Chorus (BCC) at the Strand Theatre.

Before what is anticipated to be a jam-packed house, BCC Artistic Director Anthony Trecek-King will once again lead all 12 BCC sub choirs, including the Dorchester Advanced and Dorchester Intermediate Training Choirs, which have been rehearsing this year at the First Parish Church. The 2 p.m. concert is free to the public.

In the program book, Trecek-King reviews some of the remarkable achievements of the BCC’s 2013-2014 season: “BCC won the National Arts and Humanities Youth Program Award from the President’s Committee on the Arts and the Humanities, presented by First Lady Michelle Obama. We performed two memorable concerts with our new partner at the Isabella Stewart Gardner Museum. We welcomed special guests such as Leslie Odom, Jr. and Rollo Dilworth. Our Dream a World concert was an exciting taste of BCC’s future. Concert Choir traveled to Maine to perform with the Portland Symphony Orchestra. Also, our young singers performed with poise and dignity at the recent Boston Marathon.”

Trecek-King has selected spirituals, folk songs, contemporary works, and choral music classics for the sub choirs to perform as individual groups and in various combinations. His selections balance all the livelier songs like “Come Let’s Be Merry” and “I’m Building Me a Home” with “Lacrymosa” from Mozart’s Requiem. He notes that this year’s finale features unusual blends of voices. “We have very young ones, performing with older singers, the Young Men’s singing with Concert Choir, all of which creates interesting sound combinations.”

Both Dot choirs are led by John Reynolds, Neighborhood Choir Conductor. In the Dorchester Advanced Choir are Jordan Atkins, Emma Beardsley, Carmen-Isabel Belizaire, Pierre-Zachary Belizaire, Carys Cadwalader, Francesca Callahan, Jayda Campos, Sienna Clivaz,Erica Czerwinski, Hannah Edlund, Lily Emerson Brewer, Zoe Flessas-Finocche, Christina Frederique, Emma Garvey, Grisha Gurenich, Aamaya Guzman
Rayna Hall, Sarah Henao, and Andrew Hoang.

Also, Hannah Jenkins, Christopher Lapop Salazar, Lauren Lubin, Jena Luong, James Mazas, Ross McGregor, Veronica Milun, Jack Mullin, Sophie Nerine, Annabelle Noel, Evelyn Pimentel, Mishael Quraishi, Rashida Rene,Sofia Rodriguez- Anton, Kacey Rouse, Jillian Ryan, Uma Sen, Toby Shu, Eleanor Spy,Matthew St. Louis, Helen Tang, Esther Trask, Sofia Vianna, Audrey Wang, Korena Watson, Nayarah White, Stephen Wylie-Sears, and Cindy Zhou.

The Dorchester Intermediates include Diego Argueta, Lucas Brandao, Jessica Cheng, Adoni Cruz Simms, Jade Diaz, Louisa Dillon, Soledad Dolorico-Francoeur, Daniella Du Boulay, Megan Francis, Regina Galette, Thomas Garity, Lexi Hamilton, Cole Harris, Madeleine Heckler, Benjamin Hofmann, Hannah Hummel.

Also, Sydney Jenkins, Alexandra Krupinski, Eleanor Krusemark, Emily Kuter, Julia Logan, Erica Lopez, Claire Ma, Leah Melito, Aaron Neville, Cassandra Pahre, Max Phillips, Nina Potts, Shenell Powell, Sonya Poznansky, Evelyn Reyes, Danny Rivera, Savannah Rivers, Alaya Shah, Elizabeth Spy, and Janae Vellere.

The BCC is a multi-racial, multi-ethnic arts education organization that unites area children ages 7-18 across differences of race, religion and economic status. Named Boston’s “Ambassadors of Harmony” by the Boston Globe, the BCC presents 50 performances per season in a wide range of public and private events around the world. One hundred percent of BCC alum go on to college, including Harvard, Stanford, New York University, and Berklee College of Music. To preview Sunday’s concert, visit bostonchildrenschorus.org. Reserve your seats there, too. The button says “buy” but tickets are free.