The student-led service, with the Rev. Oscar Reynoso presiding and held next door at Holy Name of Jesus Church, included prayer and remembrances of those who lost their lives when gunman Adam Lanza shot and killed 26 people at Sandy Hook Elementary School, most of them young students.
Fourth-grader Lily Vo, 10, opened the service.
"We would like to offer this Mass for the healing of Newton, Conn.," she said.
Since the school's student population varies by age, language in the service's introduction and prayer was tempered, said Angela Williams, principal of the Redlands school.
"We want to respect how parents want to communicate this to their children whether they want to talk in detail or not," she said.
When students returned to the Sacred Heart on Monday - three days after the shooting - teachers at the junior high level addressed the tragedy only if a pupil brought it up, Williams said.
If no discussion was in play, the issue would have been left alone out of respect to how the parents wanted to handle the situation.
For lower grade children, if a pupil brought up the incident, teachers would encourage them to speak with their parents, Williams said, adding, "The junior high-aged students were just in shock, just horrific shock about what had happened. And a lot of them (said), `We can't believe it. What can we do to help?"'
One way the school is looking to help cope with the loss is by creating snowflakes to send to the Connecticut school.
Williams said she received an email from a parent that mentioned the idea, and is hoping each pupil creates at least one snowflake, which would lead to more than 200 to send.
But Williams is hopeful more students will create more before they are sent in early January.
Pupils will start creating snowflakes this week and will finish upon returning Jan. 7 from a two-week break for the holidays.
The school has been known for its philanthropic endeavors.
Most recently, the students sold chips and other goods to help another Catholic school affected by Superstorm Sandy.
School staff opted not to buy Christmas gifts for one another, but instead to collect funds to help with the Sandy relief effort.
More than $1,000 was raised, Williams said.
Additional ways to help those affected by the Newtown incident are also in discussion, she said.