In the fall of 2021, experts declared a national emergency in children's mental health, urging organizations to put in place school-based mental health care services to reduce barriers and increase access to care. This paper describes implementation and acceptability of an innovative school-based model to deliver group art therapy that is integrated into the school's Muti-Tiered System of Supports, and changes in student social-emotional competencies that occurred in association with participation. The 7-week pilot was implemented in three successive semesters, serving 280 elementary students. Guardians completed Strengths and Difficulties Questionnaires (SDQ) before and after the intervention to describe changes in student social-emotional competencies. SDQ data suggest improvement in internalizing symptoms amongst participants (n = 17, mean decrease in 1.7 points [95% CI: 0.2-3.2]; p = 0.0314). Guardians surveyed (n = 12) strongly agreed that art therapy programs should be continued in the school and that the art therapy process gave their child an alternative form of safe expression [4.88 and 4.75 out of 5 (SD = 0.14 and 0.29), respectively]. All students completed the program. Cost was $170.00 per child. This school-based group art therapy model was found feasible and acceptable, and if scaled, can impact a large population of children with barriers to mental healthcare access.