modelCourse.js

var mongoose = require( 'mongoose' );

var Schema = mongoose.Schema;

var CourseSchema = new Schema({
    courseName : { type : String, default: '' }
  , description : { type : String, default: '' }
  , videos : { type : Array, default: [] }  // Pensei em deixar a ordem cresc para o video 
                                        // mais novo ficar no final e para só ir dando push nesse array quando tiver 
                                        // novos videos.
  , students: [{ type : Schema.Types.ObjectId, ref : 'Student' }]   // Alunos autorizados
  , created_at : { type : Date, default: Date.now }
});

module.exports = mongoose.model( "Course", CourseSchema );

modelTeacher.js

var mongoose = require( 'mongoose' );

var Schema = mongoose.Schema;

var TeacherSchema = new Schema({
    name : { type : String, default '', required: true }
  , courses : [{ type : Schema.Types.ObjectId, ref : 'Course' }]
  , abilities : { type : Array, default: [] }     // Habilidades em MEAN, PHP, JQuery.. para ter um info do professor
  , created_at : { type : Date, default: Date.now }
});

module.exports = mongoose.model( "Teacher", TeacherSchema );