He's considering attending the University of Minnesota in the fall and studying linguistics, something his mother thinks might be his true calling due to his love of languages.
However, while other teens at Lincoln High School in Sioux Falls, South Dakota, might be thinking right now about prom and graduation day, Lewis has been taking time off from school to appeal to the state legislature and Gov. Dennis Daugaard -- speaking out against a bill that could affect him and other transgender students.
Lewis was born a girl, but says he began to identify more as a boy when he was about 4 years old. He now lives openly as a boy, with the support of his family and friends.
The legislation -- which passed the South Dakota Senate
last week by a 20-15 vote -- says that students who don't identify as their biological gender may not use facilities designated for students of the opposite sex when those students might be present. Transgender students will instead be provided with a "reasonable accommodation" -- defined in the proposal as the use of "a single-occupancy restroom, a unisex restroom, or the controlled use of a restroom, locker room, or shower room that is designated for use by faculty."
It also orders that no "undue hardship" be placed on a school district -- possibly referring to the construction of separate restrooms -- and explains that private schools are exempt from the "reasonable accommodation" clause.
The governor told reporters Thursday that he's still going through testimony and documents, as well as considering what he's heard from the bill's proponents and those opposing it. Daugaard said he will continue deliberating through this weekend, even as hometown friends come in for a long-ago planned visit.
He must sign it into law or veto it by March 1 -- but if he does nothing, the measure will become law without his signature, making South Dakota the first state in the country to restrict bathroom and locker room use by transgender people.
"I have until Tuesday," Daugaard said of his decision. "... I want to do it well. I certainly want to do it as quickly as possible, but it's most important to do it well."
'I'm being that voice for them'
It's not clear how many transgender students there are in South Dakota. Many are afraid to go public with their gender identity for fear of reprisals and worries about alienating friends and family members.
Lewis recently appeared before a state committee to tell legislators why he thinks the proposed law would be harmful. He said he's speaking out for other transgender students at his school who are not "completely out like me."
"I'm being that voice for them," he said.
The bill makes him feel that he's "not human enough to use the bathroom with everyone else," Lewis told CNN this week while sitting at home after school, playing with his four cats. "I mean, you can make a third bathroom by isolating me with other transgender students in a place where it's easier to get picked on. It's like having to go off into the problem box."
Lewis' mom, Rachiel Reurink, said she's so proud of him.
"My son is awesome. I mean, it is so fortunate that he sees that he has support and can say 'I am in a safe place, I am going to fight for people who aren't in that place,'" she said. Her husband, Lewis' stepfather, died just two months ago, leaving her to raise Thomas and his teenage brother alone.
Meeting with the governor
Tuesday, Lewis and two other transgender people met with the Republican governor at the state capitol in Pierre to discuss the measure, an encounter requested by the Sioux Falls-based Center for Equality after Daugaard commented recently that he had never knowingly met a transgender person.
Earlier in February, according to the Argus Leader newspaper, Daugaard said he didn't feel he needed to meet transgender people before deciding the fate of HB 1008.
But after Tuesday's discussion, the governor said the meeting helped him "see things through their eyes a little better and see more of their perspective," according to the newspaper. His office also released a statement saying Daugaard "appreciated the Center for Equality group taking the time to meet with him."
Protecting students' privacy
State Rep. Fred Deutsch, who authored the bill, said the measure would help ensure student privacy.
"The primary purpose of the bill is to protect the physical privacy of students from having to expose themselves, or be exposed to others, when in a state of undress or nakedness while at school or school functions," Deutsch said.
One Sioux Falls father said he supports the measure.
"I don't think I'd want my 16-year-old boy in the bathroom with a transgender student if that student had a radically different look, like someone who changed from a girl to a boy and might have a beard now."
The parent, who didn't want to give his name, expressed concern for transgender students' security as well. "I'd also be worried with that student's safety someplace where there might be bullying."
The conservative Christian group Family Heritage Alliance Action praised the state Senate's approval of the bill last week.
"This is such the right thing to do to protect all of our students," spokesman Dale Bartscher told the Argus Leader. "It's a privacy bill, it's a modesty bill, it's sensible South Dakota common sense."
Several other states -- Illinois, Indiana, Kentucky, Massachusetts, Mississippi, Missouri, Oklahoma, Tennessee, Virginia, Washington and Wisconsin -- are considering similar legislation.
California's School Success and Opportunity Act, signed into law in 2013
, lets students participate in sex-segregated programs and activities, including sports teams, and use facilities consistent with their gender identity.
A show of support
Several dozen activists and transgender adults also came to the capitol Tuesday to show their support for the students meeting with the governor.
Nathan Leonard, a high school freshman from Watertown, said he was there to express himself in a public setting -- one of the first times he'd done so.
"This bill directly affects me and a lot of the people that will be coming in next year. It singles out transgender individuals and forces them to use something that they're not comfortable using and would also cost more money in South Dakota that we don't have," he told CNN as he stood on the steps of the Capitol with Lewis and another student, Scout Brown.
Others opposed to the measure were represented by their signatures -- 83,000 of them -- in a petition delivered to the statehouse by Heather Smith, executive director of the ACLU in South Dakota. Smith says a majority of the signatures came from people living inside the state, which has a population of about 850,000.
"I think (the bill) is dangerously harmful to students because we know there is a higher risk of suicide (among transgender people) in general, but among transgender students, there's an even higher risk. Eighty-three thousand signatures shows just how many reasons (the governor) has to veto this," she said.
The Center for Equality says 41% of transgender and gender nonconforming people have attempted suicide. "This is not because LGBT people are mentally unstable, it's because of intolerance and rejection like we are seeing by our legislature," said Thomas Christiansen, the group's president.
Stars call for action on social media
Caitlyn Jenner weighed in on the matter Tuesday, urging her almost 4 million Twitter followers to tell the governor to "veto HB1008." Actress Laverne Cox, from "Orange is the New Black," said on Instagram that the legislation "ostracizes trans students and targets them for even more harassment and bullying."
Leonard said Tuesday that despite the show of support at the Capitol, he wasn't very hopeful the governor would veto the bill.
"No, I personally don't believe he's listening to us, because we're young," he said. "He could be, but I just don¹t think he is. But he can have his opinion, and I can have mine."
Leonard and Lewis both say that part of their frustration comes from knowing there have been no problems reported among the students in their schools about who uses which restroom. "I was talking to a bunch of students at school about this bill and all of them were like, 'Why are they doing this?'" Leonard said.
Still, after spending almost half an hour with Daugaard on Tuesday, Lewis remains optimistic.
"I made the governor laugh, which is always good, but I think he got my message that at the end of the day, we all deserve respect. I think he understood that."
Lewis said he told Daugaard that he was "very lucky to have an accepting home environment and school environment that can accommodate my situation with a bathroom, but not all schools can do that."
"I'm one of the lucky ones," Lewis said.
He also told the governor the proposed law would increase the stigma against transgender students and there'd be more bullying in schools.
"I think we got to him," Lewis said. "I feel confident the governor will do the right thing. I'm not some freak who just wants to sneak into the (opposite sex) bathroom. I want to use the bathroom where I feel I belong."
Along with the rest of South Dakota, Lewis will now wait to see if the governor will side with the bill's sponsors in restricting which bathrooms transgender students can use, or veto it, leaving the current system the way it is.
"The reality of this situation is that bathrooms don¹t need to change," Lewis says. "People do."