NEW YORK -- The publisher Scholastic is rejecting criticism by two leading advocates for free expression that it committed self-censorship in halting distribution of a picture book about slavery.

The National Coalition Against Censorship and the PEN American Center last week chided the publisher for pulling "A Birthday Cake for George Washington," which had been widely attacked for its depiction of smiling slaves. NCAC executive director Joan Bertin called the decision "a shocking and unprecedented case of self-censorship."

Scholastic released a statement Monday saying that PEN and the NCAC "apparently did not correctly read" the publisher's initial announcement that it was withdrawing "A Birthday Cake for George Washington."

Scholastic said that the failure to meet company standards "for appropriate presentation of complex subject matter" was the reason for pulling the book, not criticism.