Also, for my brave Saturday Slash volunteers I will gladly do follow-up slashes (each more kindly than the next) on your query if you post them on the Query Critique board over on AgentQuery Connect. You'll get advice from me, and also people who are smarter than me. If you do post on AQ, be sure to follow the guidelines and let me know you posted so that I can follow up!
Thirteen-year-old Parker Ward never believed his little sister's stories about monsters, not until he was mistaken as one. I'm digging the hook, I'd cut "not" for flow and phrasing, and also separate it from the next para physically to give it a little more impact visually. Other than that, good job.
After Parker discovers the body of his little sister, he is inadvertently I think the fact that he's "sucked" kind of implies the "inadvertently" part, but that could just be me. sucked through a portal into a world humans are forbidden. Possible phrasing problem here - are you missing a "where" so that it reads "where humans are forbidden" or is it a world humans are forbidden to enter? It could technically work without the "where" but it tripped me up, and could be read as a mistake. He ends up "ends up" implies that the Academy wasn't his original, or intended destination, might need to rephrase. Also a lingering question - if humans are forbidden, why is he there? I realize that may be the crux of the story, but it raises the question. at Underlake Academy, a quirky, supernatural refuge from his grief, but unlike his classmates, his body parts don’t grow back. This felt kind of out of left field - do all his classmates body parts grow back? Now that everyone thinks he’s a vampire This feels like a jump from body parts growing back to vampires, hemophobic Parker must keep his identity a secret if he is to survive. Why? So he truly isn't a monster? Now he has to pretend to be one to keep from being killed? Also, is he attempting to find his way back into our world, or just rolling with the punches? And what's with dead sister? Is her body still just... lying there?
Parker adapts to this new world where valkyries blow things up for fun, Cupid’s arrows have real barbs, and the school’s favorite sport has rules against unnecessary decapitation. Awesome sentence here. Just as he starts to fit in, his sister begins to haunt him, warning him of an ancient evil threatening Underlake, determined to destroy the supernatural. Parker must choose between sacrificing himself or once again being the only survivor among all he has grown to care about. This para is great, and I love it.
Shortly after receiving my BFA and MBA, the last of my immediate family passed away. I then left for Baghdad, Iraq to work as a government contractor. These experiences were the inspiration for the parallel challenges and dangers my protagonist must overcome. I am a member of SCBWI and attended the 2012 Backspace Conference. Good bio here, not sure all the information is relevant, but I think it could fly as is.
My biggest questions are already covered in the first para above. I think you need to get the answers to my questions into that first para, which will be doable with some clever phrasing. There's some good visuals here, but get the main conflict out front - does Parker even want to go home? And is he actually human and in danger simply because of that fact?