The first thing we learn about Jess is his ambition to be "the best runner of the fourth and fifth grades" (4.2). And that's what drives him for the first several chapters of the book – being the fastest and best runner. It's something he can improve if he works really hard, that will make people proud of him, that's totally accepted in his society, and that will be seen as masculine – all pretty important things for a kid who feels like a bit of an outcast. But while he might have some ability, Jess just isn't naturally the fastest runner: he has to work really hard at it. When Leslie comes along, she easily beats him and all the others, and for all we know she never trained at it.

Jess's other, more secret ambition is to become a good artist. He has to draw because he can't help it. The encouragement of his teacher Miss Edmunds seems to be counterbalanced by his father's total disapproval. But with Leslie in his life, Jess seems to have enough permission to want to draw and to draw better. As he's talking with his new friend, "he yearned to reach out and capture the quivering life about him [but] when he tried, it slipped past his fingertips, leaving a dry fossil upon the page" (4.111). Leslie's the one who helps him see "the poetry of the trees" (4.111). With her in his life, he's able to fantasize about a career as an artist, and to start to shape a future outside of Lark Creek and beyond his parents' expectations.

More than anything, Leslie's defined by her imagination and sense of adventure. She's open and ready for anything: ready to move to a new town and make new friends, to try new things, to create something where nothing existed before. Even though moving to Lark Creek was hard on her, she wanted to do it to support her parents.

Because of her reading and the way she was brought up, Leslie is able to use her imagination and creativity, bolstered by her friendship with Jess, to get outside of Lark Creek. Terabithia is her idea:

"I know" – she was getting excited – "it could be a magic country like Narnia, and the only way you can get in is by swinging across on this enchanted rope." (4.102)

She's the one who sees magic in the ordinary, sees Terabithia where there's just a forest, and is the one who helps Jess see those things too.

We know what Jess's ambitions are, but we don't really know Leslie's. In fact, we never learn as much about her as we do about Jess, or about what Jess thinks about her. We do know she loves stories – reading them, telling them, and making them up. The girl's curious, she genuinely wants to know things, and she's a "beautiful" (3.87), naturally fast runner. But we don't really know what she wants to be when she grows up, or what drives her she's had a hard time, with only "one and one-half friends," Jess and Janice (7.111).

It's not easy being a teacher at Lark Creek Elementary – seems like the students will always find a reason to dislike them. Even though Jess thinks Miss Edmunds is beautiful and worships her, other kids criticize her because of how she appears: "the kids would make fun of Miss Edmunds' lack of lipstick or the cut of her jeans" (2.20). From this we can tell that Miss Edmunds is single, where some of the other teachers are married; she doesn't wear makeup, and she's not afraid to dress in comfortable clothing. She creates her own style and doesn't abide by public opinion. We might even say that she sounds like a feminist. Not quite sure what she's doing in Lark Creek.

But Miss Edmunds works hard to inspire her students and reach out to them. Think of the kinds of songs she teaches them in music class: "My Beautiful Balloon" (2.18), "This Land Is Your Land" (2.18), "Free to Be You and Me" (2.18, 4.14), and "Blowing in the Wind" (2.18). Those definitely encourage people to be themselves, to embrace their identities, and to be brave and inventive – songs by people like Bob Dylan and Marlo Thomas. Miss Edmunds also encourages Jess to keep drawing multiple times, calling him "unusually talented" (2.16),

May Belle is the only one of Jess's siblings that he has real affection for or tolerates. In turn, she "worship[s him]" (1.8). She's as lonely as Jess is, and also requires a friend: "I need somebody to play with," she tells Jess early on (2.4). But while she often looks to Jess to provide that friendship, for most of the book he's just not that interested, seeing her as a little squirt and preferring to go to Terabithia with Leslie.

Janice is the big seventh grade bully, the terror of the bus ride and the littler kids. She's big and mean, and at the beginning of the book we don't have much sympathy for the girl. Jess knows how to keep his head down and stay out of Janice's way, but kids as little as May Belle haven't learned that yet. Janice does things like steal little kids' Twinkies and enforce a caste policy on the school bus, where she has a special seat that nobody else can sit in.

It seems admirable and sneaky of Jess and Leslie to write a fake love letter to embarrass Janice when she's mean to May Belle, since they can't beat her up in a physical fight. It's a clever way of dealing with a problem that has to be dealt with: if Jess doesn't try to get back at Janice, he'll lose May Belle's respect.

Bill and Judy are Leslie's parents. They're both writers, and they're kind of hippies in the same way that Miss Edmunds is. They have different values from most of the people in Lark Creek, and they're more interested in being themselves than worrying what other people think. Leslie calls them by their first names, which seems really weird to Jess. They seem to treat Leslie more like an equal and another adult than their child. We never hear of them have any problem with Leslie suddenly adopting a puppy, or going to church with her friend, or spending so much time out of the house unsupervised in general.

Judy's pretty absent-minded, especially when she's working on a book project. Bill's a bit more present – and Jess observes that Leslie, accordingly, loves being with her father – but he knows more about culture than, say, practical things. They operate at a level that seems pretty foreign to Jess, with conversation about "French politics or string quartets […] or how to save the timber wolves or redwoods or singing whales" (4.136). This is a language Leslie "speaks" too, and it's a big contrast to the total absence of conversation at Jess's home, which is usually filled with the sounds of television.

Mr. and Mrs. Aarons are Jess's parents, and they're both kind of ciphers, or blanks. We don't get a sense of knowing them that well. In fact, you might realize that we never even learn their first names. This puts them in marked contrast to Leslie's parents, who are identified to us most often as Bill and Judy – on a first-name basis. This lack of first names makes Mr. and Mrs. Aarons seem almost like archetypal figures, or as only parents – we see them most often described as "mom" and "dad" – and less like individuals.

Because we see them through Jess's eyes, which show us neglect and absence – the kinds of flaws we're quick to hold on to – it's harder to see their good qualities or their love for Jess, compared to how they treat his sisters. It seems like Jess never gets the love or acknowledgement he craves from his parents.

Brenda Sue, Ellie, and Joyce Ann are three of Jess's sisters, none of whom he really enjoys associating with. Brenda and Ellie are older and the best word to describe them is "obnoxious." They don't spend time with Jess and the younger kids, or even really notice them – that is, unless they see potential for mockery, complaining, or sensation. The two older sisters aren't imaginative, or interested in expanding their minds, and there's never any hint of an idea that they would be interested in being friends with Leslie. Here are the things they do like: shopping and boys.

Ellie is smarter than Brenda – she's the one who knows how best to manipulate their mother and sucker her into giving them money. She's also the one to take the lead and let Brenda know when enough's enough. Brenda's less clever and, perhaps because of this, meaner. She made fun of Leslie for wearing boys' clothes and not acting feminine enough.

In contrast, Joyce Ann, the youngest, is treated by everybody as a baby, because she is. She's just too little to do very much, or really be very interesting. However, she's open and impressionable whereas Ellie and Brenda are harder and formed. This might be why Jess says Joyce Ann could maybe come to Terabithia, several years in the future, but never considers telling Brenda or Ellie about it.

Mrs. Myers is Jess and Leslie's fifth grade teacher. The first thing we hear about her is that she's super nice-acting on the first and last days of school – those are supposedly the only days she smiles – and the rest of the time she's really strict and hardcore. For the first portion of the book, it seems as though this is true. With her strictness and severity, Mrs. Myers comes off pretty poorly in comparison to Miss Edmunds. She favors Leslie a little because, let's face it, Leslie's a fantastic student who turns in work well above the quality of what the other students produce. But praise from Mrs. Myers just gets Leslie the wrong kind of attention.