The Secret School Invasion by Pamela Butchart (Paperback)

Izzy's school is being merged with St Bartholomew's Primary, their greatest rivals! What will happen when the new kids join, in their too-shiny shoes and with their too-loud singing? And what if they've got a secret mission and that mission is a BAD mission? Only Izzy and her friends can discover the truth, even if they must go SO DEEP UNDERCOVER that they might not come back.