It is hard to believe, but the word “everyone” is singular.
It sounds as though it should include a lot of people; in fact, it should include everyone—and that sounds plural.
But “everyone” is in the list of singular indefinite pronouns, which are listed here: each, every, either, neither, no, one, no one, everyone, someone, anyone, nobody, everybody, somebody, anybody, nothing, everything, something, anything.
I grouped them by their endings: -one, -body, and -thing. You also could list most of them by their beginnings: no-, every-, some-, and any-.
This week’s blog, which is another in a series of grammar tutorials, includes an infographic to teach the material, an exercise for your students, and answers to the exercise.