Love it. GREAT voice. Love the physical sensations mixed with quick, immediate thoughts.

Oh, you know I’m a fan of punctuating these paragraphs with noises. I can almost feel the thumps vibrating through me. GREAT.

Nice use of vocab, too. “Freak extraordinaire.” Yep. I’m calling this one “perfect” too! YAYAYAYAY!!!!!

Okay, that made me feel physically ill. GREAT job, very evocative, very intriguing voice.

I think you could tighten the first paragraph a little more, those first few sentences went a little back and forth. Other than that? FANTASTIC.

Loved it!

This is a strong opening. The thump-thump section? Love it! It really puts me right there with your MC. I'd love to know what happens next with her and what those flashes are all about.

IN-LINE CRITS:

I clutched my head, wincing in pain. No, please no. Not again. Why does this keep happening? (I would say the "Not again" conveys what you need so the "Why does this keep happening" is maybe a tad redundant.) The throbbing intensified. I pushed my chair away from the desk, trying not to draw attention to myself. My heart hammered with erratic beats. I flashed Mrs. Thompson a weak smile, as if I was merely going to the bathroom. (Okay, this might be entirely me, but I didn't realize she'd gotten up and was leaving. I thought she was maybe going to the bathroom...at her desk. I was all O_O and had to reread. Might be a clarification issue but if I'm the only one who's ever read it this way, then it's probably just my crazy brain!) She eyed me curiously (removed comma) but didn’t pause in her lecture on mythology.

I ducked into the hallway and leaned against the wall. Bending over and bracing my hands on my knees, I took a deep breath. Searing heat pooled in my stomach. (Great line.)

Don’t throw up. It’ll pass. Calm down.

Another breath. Another. It didn’t help.

The light above me flickered. A harsh thumping echoed in my ears, (added comma) and images flashed in my mind. Each sound conjured a new picture. (I think the thump-thump conveys this effectively and makes this sentence not-so necessary.) My eyes stung with fresh tears. I covered them, trying to block out the pain and panic.

Thump.

Mobs of men attacked each other.

Thump.

Fires ravaged forests, fields, and cities.

Thump.

Livestock covered in black sores died where they fell.

Thump.

A gentle hand touched my shoulder. “Are you alright?” a voice asked.

The pain stopped. My pulse calmed, and my (added comma and "my") stomach settled. The images and drumming ceased. I sighed in relief and uncovered my eyes to see a boy I didn’t recognize.

“I’m fine.” The words were barely coherent. I straightened. My cheeks warmed, (added comma) and I wiped my eyes before hurrying back into the room, wishing I could run much farther away. Being branded some freak extraordinaire was the last thing I needed right now.

Holy crap, this is good. Loved the voice. My heart is still pounding. I have nothing else to add to the others' comments.

This title totally made me want to read this before I even knew what it was about so YAY for awesome titles.

I'm a HUGE fan of all things dark and creepy and this opening definitely made me want to read further.

I feel like this is almost perfect--ALMOST. It just needs a bit more. Is this something frequent that happens?

Also and I know this is only the first 250, but I don't know if your MC is a boy or girl and that's not good. The reader should definitely know the sex of the MC within the first 500 words.

Always ask these questions to yourself whenever you can when you're weaving suspense into a novel. Who, How, What, Why When?

Yes it is very important not to info dump. You never want to reveal too much. But is also very important that the reader knows a little bit right off the bat because it adds to the suspense and the build you should be weaving through the entire novel.

Other than those few things, great job!