The rating is completely inappropriate. Not only are the concepts dark and deep for this age group, this movie is scary, once uses the word “hell” as in …”what the hell”, shows terrifying imagery of dentist with drills and a brief “murder clown” (as they call it). The introduction of the “sleep” character shows the character using a pillow over faces of people to put them to sleep, next scene is the character using a hammer to smash a baby to sleep — this was dangerous imagery for my young children as they learn safe ways to play with our newborn, and countered our “safe play” parenting. Overall - would be better for older kids.
IMO Y7 should mean that you can let your kid watch it with little supervision, or without explanation or helping them through it. This requires intermittent fast forwarding and engaged coaching to be okay for a Y7 audience.