You've a good plotline developed here, Scrivener. It's entertaining and believable enough to keep the reader engaged. I hope the suggestions I offer will help parts of the chapters unfold more effectively. These are, of course, suggestions, to accept or reject as you wish. Here are a few observations:
"I think our teacher, Mr. McGregor, said people back then weren't [I think he wouldn't have said "our teacher". It indicates the author's need to provide info to the reader.]
With their youthful curiousity getting the better of them, [...their youthful CURIOSITY ... >> I don't believe yours is the UK spelling.]
The teenagers were now intensely frightened; [can you show their fear, rather than tell the reader about it?]
"You okay, Ben?," Sean asked. "Yeah, you?," [You shouldn't have a comma after the two question marks.]
Will look forward to the remaining chapters.