The families remain anonymous in the lawsuit, which alleges that the assaults date to 2013.
The lawsuit, filed in D.C. Superior Court last week, alleges that since at least 2014, multiple reports of Fernandez acting suspiciously around the children should have triggered the school to fire him.
Principal Cristina Encinas, LAMB Executive Director Diane Cottman and Fernandez are named in the lawsuit. Encinas left her post in December after an internal investigation, and Cottman is expected to step down at the end of the school year.
A spokeswoman for the school said LAMB's board of directors had expected a lawsuit could be coming and has been working with its insurance company for months in preparation.
"We hope to work toward a just resolution of all claims," school spokeswoman Dawn Arteaga wrote in an email. "The board has been working diligently to do everything in their power to ensure that LAMB will continue to be a top-performing Tier 1 school for many years to come."
Cottman did not immediately respond to a request for comment, and Encinas declined to comment.
Fernandez taught at the Northeast D.C. campus of LAMB, which also has two campuses in Northwest D.C. The school is one of the most highly regarded in the District, with 462 students enrolled in preschool through fifth grade and nearly 1,200 students on a wait list to enroll in 2017 — one of the longest in the city.
In 2014, a neighbor living across from the school said they saw Fernandez playing with students during recess in an "inappropriate manner," the suit alleges. The school reportedly did not investigate the allegation.
Staff members, according to the lawsuit, also saw Fernandez taking children into the school's basement alone — something teachers are prohibited from doing. The parents said in the lawsuit that they told the school's principal that Fernandez sent their elementary-aged children excessive emails and interacted with them frequently.
The school suspended Fernandez in 2015 while police investigated him, and when authorities found no wrongdoing, LAMB officials reinstated him, the lawsuit says. He remained the teacher of the students in the lawsuit until they graduated from the fifth grade in 2015, and he was allowed to chaperon students on field trips, when the lawsuit alleges he abused other students.
Fernandez came under investigation again in 2017 after the children involved in the lawsuit told their parents about the abuse. Although family members did not know about the abuse until then, one family said their child had displayed signs of trauma since 2013.
"Minor 1 began exhibiting unusual behavior, including, but not limited to, becoming upset, suffering from an eye twitch, having trouble sleeping, waking up agitated, and being afraid of being alone in Minor 1's basement, taking a shower or going to the bathroom alone," the statement says. "Minor 1 also began suffering from anxiety, having trouble breathing and was sad and despondent."
The lawsuit also alleges that Encinas and Cottman failed to inform the families about the full scope of the allegations against Fernandez. The parents, for example, knew about one incident in which Fernandez was spotted with children in the basement. They did not know that someone in 2015 reported that Fernandez was in the basement another time with their children with the door locked for 20 minutes.
In December, the school released findings of an internal investigation, which found that the "administrators in charge failed to respond appropriately," according to a letter the school sent to parents at the time.