My Teacher Is an Alien Series by Bruce Coville

Sixth grade is just out of this world!Susan Simmons can tell that her new substitute teacher is really weird. But she doesn't know how weird until she catches him peeling off his face -- and realizes that "Mr. Smith" is really an alien! At first no one will believe her except Peter Thompson, the class brain. When Peter and Susan discover Mr. Smith's horrible plans for their classmates, they know they have to act fast... moreSixth grade is just out of this world!Susan Simmons can tell that her new substitute teacher is really weird. But she doesn't know how weird until she catches him peeling off his face -- and realizes that "Mr. Smith" is really an alien! At first no one will believe her except Peter Thompson, the class brain. When Peter and Susan discover Mr. Smith's horrible plans for their classmates, they know they have to act fast. Only they can get rid of their extraterrestrial visitor -- and save the rest of the sixth-grade class from a fate worse than math tests! less

Brains are sizzling in the seventh grade...The first day of seventh grade is probably the worst day of Duncan Dougal's life. He knows that things are really bad when he finds an alien's hand in a dumpster and then gets plugged into an alien brain fryer!Can Duncan find out which of the four new teachers in his school is an alien before his brains get fried to a pulp -- or before the aliens try to fry the whole planet?

Kidnapped in Space?Peter Thompson has had some pretty weird teachers in his time. By the time he discovers that his newest teacher glows in the dark, he’s flying away from Earth in a spaceship full of aliens and there’s no one he can call. How do you report an alien to the F.B.I. anyway?Before Peter can do anything, he’s taken on the strangest field trip of his life! His friends, his father, his school are suddenly a million miles away!

ALIEN INVASION OF EARTH!Peter Thompson, a typical seventh-grader, finds himself touring the planet with his friends Susan Simmons and Duncan Dougal, and three aliens in disguise! Their mission? To file the final report that will determine Earth's future in the universe. As the clock ticks away the hours before their meeting in space, the tour becomes weirder and weirder... moreALIEN INVASION OF EARTH!Peter Thompson, a typical seventh-grader, finds himself touring the planet with his friends Susan Simmons and Duncan Dougal, and three aliens in disguise! Their mission? To file the final report that will determine Earth's 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 Julie"-- the weirdest alien yet! Meanwhile, Peter discovers a secret hidden for decades. Will his discovery save the Earth, or is it already too late to stop the aliens from destroying the planet? less