Young adult and middle grade science fiction

I’m going to be on a panel in a few months about YA and middle grade SF. The basic premise of this panel, according to the organizers, is that there is barely any YA SF out there.
I would beg to differ. It’s just much, much cooler and more contemporary than most of the adult SF I’ve read.
Admittedly, I haven’t read much SF lately, because the Old Guard of SF turns me off. It just doesn’t feel contemporary to a modern world anymore–it feels like many of them are still writing from the perspective of the 60s or the 80s. But I also admit that I haven’t explored much in that genre since early in college, so I’m willing to be given some good examples of things that read like, for example, Scott Westerfeld.
So, I’m on the hunt. I just know there’s a LOT of great science fiction out there in YA right now–not as much in middle grade, but some there too. Granted, yes, there is definitely a lot more fantasy than science fiction, because fantasy is in the ascendancy, but there’s a lot more good SF out there than most people who lament the lack of it know. Here’s my adm
ittedly short list so far.
Life as We Knew It by Terry Miller Shannon
The House of the Scorpion by Nancy Farmer
Feed by M.T. Anderson
Uglies by Scott Westerfeld
Pretties by Scott Westerfeld
Specials by Scott Westerfeld
Peeps by Scott Westerfeld
The Last Days by Scott Westerfeld
Midnighters: The Secret Hour by Scott Westerfeld
Midnighters: Touching Darkness by Scott Westerfeld
Midnighters: Blue Noon by Scott Westerfeld
Among the Hidden by Margaret Peterson Haddix (and the rest of the Shadow Children series)
Turnabout by Margaret Peterson Haddix
After by Francine Prose
Gathering Blue by Lois Lowry
Messenger by Lois Lowry
Things Not Seen by Andrew Clements
The Sterkarm Handshake by Susan Price
City of Ember by Jeanne Duprau
People of Sparks by Jeanne Duprau
Prophet of Yonwood by Jeanne Duprau
Also granted, most of these are social science fiction/dystopic, which most hard SF people don’t count as actual SF. I do. So perhaps the point is that there’s not as much S
F in young people’s literature that depends on hard science, explores space? Okay, I can grant you that.
Relatively older (great that they’re still out there, but what other newer ones do we have?)
Dragonsong by Anne McCaffrey (yes, I count this as SF–there are dragons, but the whole story happens because people came from Earth on a spaceship to this planet)
Tuck Everlasting by Natalie Babbitt (well, kind of. It’s more a fable than anything, but the idea is of living forever through time, and somehow that feels like an SF theme to me)
A Wrinkle in Time by Madeleine L’Engle (my favorite all growing up)
Many Waters by Madeleine L’Engle
A Swiftly Tilting Planet by Madeleine L’Engle (and pretty much all her other books, too)
The Devil’s Arithmetic by Jane Yolen
The Giver by Lois Lowry
Shade’s Children by Garth Nix
The Ear, the Eye, and the Arm by Nancy Farmer
Rats by Paul Zindel
So, I’m looking for a list, and I’m looking for recommendations in adult science fiction that might feel contemporary to a teen–nothing that the Old Guard would praise because it “reads like Heinlein!” Your thoughts?