Brain Juice

Brain Juice was the twelfth book in the Goosebumps Series 2000 book series. It was preceded by Attack of the Graveyard Ghouls, and followed by Return to HorrorLand.

Plot
Two dumb kids are always being taunted by the smarter kids, so they ask their uncle, who is a scientist, to give them something to make them smarter. He gives them a placebo, grape juice, but two aliens who are looking for slaves switch it with actual brain juice. That makes the children so smart, that they are kicked out of school. Now the two children must try and escape the alien's clutches.