When Gavin Grimm transitioned after his freshman year at high school, he was finally starting to feel comfortable -- to like school -- a place where he had previously felt he couldn't be himself. He'd been granted access to the boys' bathroom, and his principal approved. Everything seemed to be working out.

After just two months, though, complaints from parents started pouring in, saying they didn’t want a "girl" using the boys' restroom. So Gavin was barred, and left disillusioned and disappointed with his school’s policy. "It turned into a super scary, horrible place," Gavin tells MTV News. "I basically lost motivation to do anything."

But he wasn’t down for long.

Now 16, Gavin is fighting back against Gloucester High School in Virginia -- with help from the ACLU -- suing them for what he says is his "right" to use the boys' bathroom. The rising junior opened up to us about why this legal journey is one he’s willing to see through until the very end and how a teenager ended up waging a major court battle:

'In freshman year before I had transitioned in school, I was really uncomfortable.' I just saw [school] as a really bad place to be. And there weren’t really a whole lot of issues -- I’d been bullied in school for most of my life, but I [hadn't] been in high school. Even though I wasn’t bullied [at] all in freshman year of high school, it was just a horrible place. I didn’t want to go, because I couldn’t be myself.

I didn’t even finish freshman year in public school -- I actually dropped out in the second semester. I did an online program instead because I wasn’t out and it was really taking a toll on me. But then, in sophomore year ... I was able to come out [April 23rd of 2014] and live and go to school as myself.

After I transitioned in school ... it [became] this place I [could] be myself and it was really great, especially when I was able to use the boys' bathroom, for that period of time I was allowed to do so. Then, after I was barred from that, it turned into a super scary, horrible place. I basically lost motivation to do anything.

It was really hard for me to pull through the last quarter [sophomore year], especially. My grades took a little bit of a dip. I just felt like, I didn’t have a place there. If you don’t even have a bathroom that you’re allowed to go to, it’s just an upsetting foreboding place. (At press time, Gloucester High School had not responded to MTV News' request for comment.)

'When the ACLU contacted me, they seemed to think I definitely had a legal grounds to which to fight this.'

I don’t know, in fact, how the ACLU [found me]. I think some unnamed third party contacted us or contact them or something like that, someone who was on my side and though it would be helpful. I think that’s what happened.

For me personally, the reason I even said, “Ok, let’s take this legal grounds,” was because it really at the time, it wasn’t an option. It wasn’t something I made the conscious decision to do; it was naturally [something] I’m going to continue with, because I can’t rest just not having a bathroom. That wasn’t an option.

[Where it stands now is], the judge said he’d submit a written opinion and the opposition has 21 days to submit an answer and the trial date will be set. There is no word when he’ll submit the written opinion and, of course, everything else follows that.

'I've got to look at it from the standpoint that I’m helping people, because this is not something I would have ever wanted to do.'

I don’t like being so public with everything, especially about something so personal. I do see that I have the opportunity to help people, in the position I am in. Just for the fact I am able to help people’s lives in a positive way has made it worth it.

'It’s just a fundamental human operation to use the bathroom.' To think there’s any individual that has an obstacle regarding that is absolutely preposterous to me. It’s something that should have never, ever have happened. It’s just something that’s a basic human right. And that people don’t have it is just abhorrent and it’s not acceptable.