Mandie and the Schoolhouse's Secret

is the twenty-sixth book in the Mandie series.
==Book Description==
When Mandie is exposed to the measles, Grandmother Taft keeps her out of school until they know for sure she doesn't have the disease. Mandie doesn't like missing out--especially with all the construction to modernize the school building going on. Surely there's a mystery to investigate!
(Description from Mandie.com)