What is the name of this Scholastic Children's book? About 2 girls that almost turned into babies?

It was for sale in a school book sale order form flier around the year 2003.

What is the name of this Scholastic Children's book? About 2 girls that almost turned into babies?
I think you might be talking about Turnabout, by Margaret Haddix. Below is part of the summary and the link is to a 2007 copy. It's been reprinted and there are other copies available (some even going for 1 cent on Amazon.com).





Eighty-five years ago, Melly and Anny Beth were old women participating in a highly secret research study that reversed the aging process. However, the directors of Project Turnabout couldn't halt the reversal, and the women have "unaged" back into teenagers. Soon they will become so young that they will no longer care for themselves. Even worse, a reporter's interest in Melly is threatening to destroy the privacy that the teens alone still value in the publicity-mad culture of the year 2085. The suspense is unflagging as the two flee from unwanted exposure and search for a way to live out the rest of their days.
Reply:Turnabout by Margaret Haddix.

lady slipper