Bruce Coville 
My Teacher Flunked the Planet [EPUB ebook] 

Alien Invasion of Earth! Peter Thompson, a typical seventh-grader, finds himself touring the planet with his friends Susan Simmons and Duncan Dougaland three aliens in disguise! Their mission? To file the final report that will determine Earths future in the universe. As the clock ticks away the hours before their meeting in space, the tour becomes weirder and weirder. The three friends come face-to-face with a plague of poots and Big Juliethe weirdest alien yet! Meanwhile Peter discovers a secret that has been hidden for decades. Will his discovery save Earth, or is it already too late to stop the aliens from destroying the planet?