Hey kids, school holidays are nearly over and to prove it here come the barrel-scraping dregs of the summer season. This time, it’s teen assassins attempting to make it in high school, as Hailee Steinfeld turns her back on the secret service and sets her sights on the prom. Samuel L Jackson is the former trainer who teaches her everything about killing but nothing about adolescent relationships. The film unwisely nods its head towards Mean Girls and Clueless, but (like Jackson’s recent misjudged adventure Big Game) can’t seem to make up its mind about the age or desires of its target audience. From the grisly punning title to the low-rent action sequences, this really is less fun than double maths.