I am glad that you enjoyed Pendragon.
Now you will want to continue through the series.
The next book is
Pendragon The Lost City of Faar.
Here are some suggestions to try…
Remembering Raquel by Vivian Vandevelde.
Various people recall aspects of the life of Raquel Falcone, an unpopular, overweight freshman at Quail Run High School, including classmates, her parents, and the driver who struck and killed her as she was walking home from an animated film festival.
Cures for Heartbreak by Margo Rabb.
The Shadow Thieves by Anne Ursu is part of a series (The Chronus Chronicles) so you may be interested in book 2, The Siren Song, if you haven’t already read it. Since you mentioned liking historical fiction and since The Shadow Thieves (and Percy Jackson) have mythology, I’ve included some books below that have both of these and also a couple with a little fantasy/magic. Here are some other books that I hope you will like:
It depends on what elements of sociology and psychology and what ages/grades you are interested in. However, here are some that you
might find useful for teens of various ages (both Giles and Hautman tend to write psychological fiction for teens). I hope these help--
Invisible by Pete Hautman (mental illness).
Doug and Andy are unlikely best friends--one a loner obsessed by his model trains, the other a popular student involved in football and
theater--who grew up together and share a bond that nothing can sever.
I have some suggestions if you liked A Walk to Remember, and The Notebook.
A Northern Light by Jennifer Donnelly.
In 1906, sixteen-year-old Mattie, determined to attend college and be a writer against the wishes of her father and fiance, takes a job at a summer inn where she discovers the truth about the death of a guest. Based on a true story.
A Great and Terrible Beauty by Libba Bray.
Here are some other titles that you might consider. There are two more titles in that series.
Frostbite by Richelle Mead.
Rose loves Dimitri, Dimitri might love Tasha, and Mason would die to be with Rose...
Madapple was a finalist for the American Library Association Award, and I’m on the waiting list to read it.
Here are some other titles you may enjoy:
A Curse Dark as Gold by Elizabeth Bunce.
Upon the death of her father, seventeen-year-old Charlotte struggles to keep the family's woolen mill running in the face of an overwhelming mortgage and what the local villagers believe is a curse, but when a man capable of spinning straw into gold appears on the scene she must decide if his help is worth the price.
Another book by James Howe that you may enjoy is The Misfits. The book is about four students who do not fit in at their small-town middle school and decide to create a third party for the student council elections to represent all students who have ever been called names.
Here are some other books you might like to try:
If you liked East by Pattou, you might like these.
Beauty by Robin McKinley.
Kind Beauty grows to love the Beast at whose castle she is compelled to stay and through her love releases him from the spell which had turned him from a handsome prince into an ugly beast.
The Goose Girl by Shannon Hale.
On her way to marry a prince she's never met, Princess Anidori is betrayed by her guards and her lady-in-waiting and must become a goose girl to survive until she can reveal her true identity and reclaim the crown that is rightfully hers.
I have some suggestions if you liked Secret of the Sirens by Julia Golding:
The gorgon's gaze by Julia Golding.
Mallins Wood is home to the last surviving gorgon, and Col's mother, the gorgon's supernatural Companion, is determined to save it from encroaching development--even to the point of endangering Col and his best friend Connie, the most powerful Companion alive.
The chimera's curse by Julia Golding.