Jack has a big old crush on Mertie-Jo, so it's clear she's the closest thing to a romantic interest we get in Dead End in Norvelt. We can almost see him melting when she unleashes her signature head-tilting move, and he gives her his "handsome smile—the one where she couldn't see [his] missing tooth" (10.111).
It's clear nothing is going to come of this crush, though, because Mertie-Jo seems to be at least one league out of Jack's. (Not to mention, she's kind of a meanie.) He admits that he "allowed [himself] to like her too much because I just knew she would never like me back" (10.111).