Then, to his dismay, in March the school district notified Lanigan they would only pay for $60,000 of his legal fees -- he incurred more than $120,000.
And last month, he was destaffed from South Lakes -- a decision based on seniority and enrollment numbers.
The school simply didn't have the enrollment to staff nine P.E. teachers.
His wife Karin is working part-time in order to help take care of their children who range in ages from 8 to 14. She left her fulltime position when Lanigan was transferred to Reston.
Despite all of these hardships, the Lanigan family doesn't plan on leaving the area -- both Lanigan and his wife were born and raised in Northern Virginia and their parents are still there too.
Uprooting, he says, would be a major disruption.
Until The Washington Post's Saturday article highlighting Lanigan's present-day difficulties, several families in their housing development had assumed the Lanigan family was doing O.K.
But Beth Tweddle, 50, a neighbor who has known the Lanigans for more than 10 years, said his inner circle knew better.
The pain of being falsely accused hadn't diminished: she watched as Lanigan lost weight, his trademark "booming" laugh fading away.
"After the exoneration we heard that laugh again," said Tweddle. "It was so great a year ago for it to come back again. But it's been diminished."
When asked if he would consider suing the accuser's family, Lanigan said, "I just don't know."
Right now, he says, his focus is on trying to get his money back and securing a job.
The Lanigan family has taken out loans to make ends meet, so they've set up a fund to help pay off the legal bills.
Lanigan is also picking up work as a soccer trainer at a soccer club.
"Hopefully," Tweddle said, "Sean's laugh will be back soon."
For now, Lanigan and his wife are staying strong. They celebrated their 16th anniversary last Friday, and Lanigan says they're closer than ever: "one strong, unified mind."
"We've always taught our kids right and wrong, and … there are people out there that are trying to make this thing right," he said.