Static Method in School Catalogue Task

I’d be very grateful for anyone to cast over this.

I’ve got a static method within a the parent class, but when I call it return an error:

catalog/app.js:34
return substituteTeachers(randomNumber);
^

TypeError: substituteTeachers is not a function
at Function.pickSubstituteTeacher

This is the code in isolation:

static pickSubstituteTeacher (substituteTeachers) {
const randomNumber = Math.floor(substituteTeachers.length * Math.random());
return substituteTeachers(randomNumber);
}

And this is all the code for the project:

class School {
  constructor (name, level, numberOfStudents) {
    this._name = name;
    this._level = level;
    this._numberOfStudents = numberOfStudents;
  }

  get name() {
    return this._name;
  }

  get level() {
    return this._level;
  }

  get numberOfStudents() {
    return this._numberOfStudents;
  }

  set numberOfStudents(value) {
    if (value === 'String') {
      return 'Invalid input: numberOfStudents must be set to a Number'
    } else {
      this._numberOfStudents = value;
    }
  }

  quickFacts() {
    console.log(`${this.name} educates ${this.numberOfStudents} students at the ${this.level} school level.`);
  }

  static pickSubstituteTeacher (substituteTeachers) {
    const randomNumber = Math.floor(substituteTeachers.length * Math.random());
    return substituteTeachers(randomNumber);
  }
}

class PrimarySchool extends School {
  constructor (name, numberOfStudents, pickupPolicy) {
    super(name, 'primary', numberOfStudents);
    this._pickupPolicy = pickupPolicy;
  }

  get pickupPolicy() {
    return this._pickupPolicy;
  }
}

class HighSchool extends School {
  constructor (name, numberOfStudents, sportsTeams) {
  super(name, 'high', numberOfStudents);
  this._sportsTeams = sportsTeams;
  }


  get sportsTeams() {
    return this._sportsTeams;
  }
}

const lorraineHansbury = new PrimarySchool('Lorraine Hansbury', 514, 'Students must be picked up by a parent, guardian, or a family member over the age of 13.')

lorraineHansbury.quickFacts();

const sub = School.pickSubstituteTeacher(['Jamal Crawford', 'Lou Williams', 'J. R. Smith', 'James Harden', 'Jason Terry', 'Manu Ginobli']);

const alSmith = new HighSchool ('Al E. Smith', 415, ['Baseball', 'Basketball', 'Volleyball', 'Track and Field']);
console.log(alSmith.sportsTeams);

alSmith.sportsTeams;


the error is pretty helpful? It involves this line:

    return substituteTeachers(randomNumber);

substituteTeachers is an array, you attempt to call the array function. You should use the randomNumber as index to get a value from the array, how do we do this?

Square brackets.

Thank you!