Hidden Valley High is exactly the type of place you'd think would be called Hidden Valley High. It's a towering glass-and-brownstone structure in the middle of Manhattan, plastered with posters reading Is Your Child Gifted? and Accelerate Your Studies And Be Happy! There was nothing really 'hidden' about it. (Or 'valley,' for that matter.) All I knew was that it was modern and pretentious-sounding. It had a Starbucks on campus and like three indoor pools. Also, adding to the misery, I was about to start the first of one-hundred-and-seventy days locked within its shining glass walls, still sparkling from this morning's window scrubbing.

I figured I should get it over with, and I jogged up the steps without tripping once.

—

My first period of the day—AP Environmental Science, according to the crumpled-up schedule stuffed in my back pocket—took place in the world's most humid science lab. I have no idea why the teacher chose to have the dingy classroom right next to the second of the three pools and not, like, the shiny tenth floor classrooms with the ocean view, but I guess there's something for everybody. People were already inside, milling around in that indecisive way when they don't know who to sit with or what to do or what day of the week it is. A couple kids were already smirking in the back corner, near the lab tables—probably kids who had known each other since fifth grade, or something, and had never changed schools. Or friends. I wondered how they could do that.

Just then, somebody tapped my shoulder. "Hey man, were you gonna sit there?"

He pointed to the seat I was idling in front of. He was tall, even taller than me, with choppy sandy blonde hair and roguish good looks like a California surfer. Though his eyes were playful, they were marred by a giant scar that raked down his face, ending in a nasty bump on his chin. The look was an unsettling contrast with his cargo shorts and tight-fitting t-shirt, which framed his athletic body.

"Luke," said the guy, holding his hand out good-naturedly. If I had done a double-take, he didn't seem to notice. "Sorry. I should have started with that."

"Oh, no, you're cool," I replied quickly. I took his hand. "Percy Jackson."

"So, Percy Jackson, were you planning on occupying this seat here or should I be joining the sheep over there?"

"No, you can have it, I was just standing here." I shouldered my backpack out of instinct, not that there was anything to put in it.

Luke grinned, dropping his books in a thump on the desk. He pulled out the chair, collapsing on it casually, and heaved an exaggerated sigh. "Always gotta take the corner back seats. Old Posey never sees you if you're in the back." He took another look at me. "You new here at this beloved institution?"

I nodded and gestured to his pile of stuff. "I don't even know where you got those books." Meaning: It's the first day of school. Why do you even have those?

"You'll be fine. I'll get someone to show you around. Hey, Grover!" The last statement was directed somewhere away from me, probably at the throng of indifferent-looking teenagers waiting for the bell to ring. One emerged from the pack—a short, curly-haired boy with an oversized Rasta cap, almond-shaped brown eyes, and a cheerful smile. He couldn't have been more than seventeen, but he was cultivating an impressive goatee on his chin.

As he came into full view, I realized belatedly that he was limping: he had a leg brace on over his jeans. I gave him an apologetic smile as he struggled to get past a gaggle of giggling girls, who were too focused on some Instagram to make way for him.

Luke nodded at me. "Grover, this is Percy Jackson. He's new here. Figure you can show him around?"

I grinned and held up a hand. "Hi. I'm Percy," I said, extending my hand.

Grover grabbed my hand and shook it vigorously, and for a second it occurred to me how cold Luke's hand was by comparison. "Hey there, Percy, so nice to meet you! Yeah I can show you around, be happy to. Class is gonna start in"—he looked up and around confusedly, then glanced quickly at his watch—"like a minute, though, so I'll just find you after class. What's your next period?"

"Uhhhhhhhhhh English Four honors. With, uh—?"

"Halkias!" beamed Grover. "Ms. Halkias is the nicest teacher on this campus. You'll love her."

"Ay ya ya! She's a fiery one," shouted Luke from the chair, and he mimed fanning himself.

Grover didn't look back at him. "Luke has a thing for her but I don't think he realizes it's illegal," he said without smiling. I laughed, and after a second he broke and started laughing too. Grover was the kind of guy who just made himself comfortable with you, and by some black magic, you felt just as familiar with him. If anyone could get me through this school year, I hoped it was Grover.

"Anyways," Grover continued, "I have English with you next period, and so does Luke. And a couple other kids in here. I'll walk you, let you see the sights. Cool?"

"Cool." We shook on it right as the bell rang.

Everyone stilled. There was a second of bated silence, and then THWACK! The door burst open and the smell of the pool next door came pouring in again. Along with the humidity came a man, lean and tan and tall, with salt-and-pepper hair and the brightest green eyes I'd ever seen. He was wearing flip flops, khakis, and a blindingly colorful Hawaiian shirt with a pin that said Don't Panic! I liked him instantly.

"Hello, A-P-E-S class of 2019!" he bellowed. The class laughed unsurely and parted in front of him as he strode in. I wondered if I was supposed to cheer.

"My name," said the man as he took his place at the front of the class, "is technically Mr. Posey, but you can just call me Posey. I'm your AP Environmental Science teacher this year, as I will be for many others in many other years. I see you are all standing awkwardly waiting for me, like sea cucumbers on a bumpy rock. Ha! Ha! I laugh at my own jokes sometimes, you'll get used to it. Anyways here's a seating chart I made five minutes ago."

Oh my god. I could get used to this.

The class started milling around to find their seats, so I had to pick my jaw off the ground and follow them, but believe me when I say I'd never been more excited about a teacher. I found my chair near the front and waited for the rest of the class to get organized.

A girl slid in next to me. Somewhere between emo and punk, she looked as if 1998 had never died. Her backpack clinked with dozens of band pins that I'd never seen before, and her eyes—stormy, shocking, electric blue—were lined with jet-black eyeliner. A silver circlet crowned her spiky hair, and I was just about to wonder what it was until she looked right back at me.

I raised my eyebrows at her when she started frowning.

After a long second, I broke the silence. "Uh, hi, my name is—"

"Percy Jackson, right?" she asked suspiciously.

I blinked in bafflement. "I mean yeah. Yeah. Wait, what? Who are you?"

"Guess."

"Uh…" I racked my brain in desperation. How did she know my name? Why wouldn't I know hers? "I—I don't know. I'm sorry. I don't think I've ever seen you before." Had I?

The girl's face clouded over, and quickly she arranged it into something resembling embarrassment. "Oh, sorry, I think I heard someone say your name somewhere. I didn't mean to—"

"No, I get it, I think Luke might have shouted it like a dozen times right before class started."

She nodded and gave a light laugh, but I saw the doubt in her eyes. "Yeah, that must have been it. I'm Thalia."

"Percy." I shot finger guns at her because it was the only thing I knew how to do. "But you knew that already."