Comments on a couple of the suggestions so far:
Number the Stars, Lois Lowry - excellent choice.
The Book Thief, Markus Zusak - outstanding book, though in my opinion, possibly a bit intense for a ten-year-old (not in any particular aspect/scene, but rather overall tone, and the powerful impact from how well-written it is), but judge for your own kid. And the movie was good too.
The Green Glass Sea -- fascinating, compelling book; be aware that: (a) the level of drinking and smoking (cigarettes) by the adults involved in the high pressure Manhattan Project is undoubtedly historically accurate but may be a bit jarring to a kid today, and (b) the
(girl) protagonist is perhaps gender dysphoric, though that may go right past a boy reader.
Speaking of Shindler's List, you might consider The Boy on the Wooden Box, Leon Leyson, which is Leyson's memoir of surviving the war (age ten at the start), being saved by Schindler. (I am uncertain how well this book will work for those not already at least somewhat familiar with the Schindler story; if anyone has tried having a kid read it as a starting point, I'd be curious to hear.)
Additional suggestions:
Hero on a Bicycle, Shirley Hughes (historical fiction, Italian resistance, WWII)
Lily Renee, Escape Artist: From Holocaust Survivor to Comic Book Pioneer, Trina Robbins (biography in comic book form)
My Family for the War, Anne Voorhoeve (historical fiction on Kindertransport; really good but may speak more to girls)
Terezin: Voices from the Holocaust, Ruth Thomson (nonfiction, outstanding); and accompany it with:
Brundibar, Tony Kushner & Maurice Sendak
Resistance, Defiance, Victory trilogy of graphic books by Carla Jablonski & Leland Purvis (French resistance, interesting though probably better at around age 12 or so as some material, such as parents getting killed, may be much for a ten-year-old)
