students and teachers in a class_instruction - ruby-on-rails

Question

Setting up the database, I am just curious if I did it correctly, as it looks a bit off. There are people, who have a user account, and a role (teacher or student). they are participants in a class (where a class has many students and teachers; a student has many classes; a teacher has many classes). I think my class_instruction model is off in the DB, but please tell me if it will work, or if there is a better way (like maybe with a has_many_through table of participants)
schema.rb:
ActiveRecord::Schema.define(:version => 20130524160107) do
create_table "class_instructions", :force => true do |t|
t.string "name"
t.datetime "time"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
t.integer "person_id"
end
add_index "class_instructions", ["person_id"], :name => "index_class_instructions_on_person_id"
create_table "people", :force => true do |t|
t.string "firstName"
t.string "lastName"
t.integer "user_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "people", ["user_id"], :name => "index_people_on_user_id"
create_table "roles", :force => true do |t|
t.string "name"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
create_table "user_roles", :force => true do |t|
t.integer "user_id"
t.integer "role_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "user_roles", ["role_id"], :name => "index_user_roles_on_role_id"
add_index "user_roles", ["user_id"], :name => "index_user_roles_on_user_id"
create_table "users", :force => true do |t|
t.string "email", :default => "", :null => false
t.string "encrypted_password", :default => "", :null => false
t.string "reset_password_token"
t.datetime "reset_password_sent_at"
t.datetime "remember_created_at"
t.integer "sign_in_count", :default => 0
t.datetime "current_sign_in_at"
t.datetime "last_sign_in_at"
t.string "current_sign_in_ip"
t.string "last_sign_in_ip"
end
add_index "users", ["email"], :name => "index_users_on_email", :unique => true
add_index "users", ["reset_password_token"], :name => "index_users_on_reset_password_token", :unique => true
end
My concern is that the person_id is part of the class. Is this correct?
ClassInsturction.rb :
class ClassInstruction < ActiveRecord::Base
belongs_to :people
has_many :cassignments
has_many :assignments, :through => :cassignments
def className
self.name
end
def classAssignments
return self.cassignments
end
end

Answer 1

I would make a joining table that has both class and people and use has many through. If people have many classes and classes have many people you can not do this any other way.

Answer 2

I have seen usually belongs_to with singular form:
belongs_to :person
I am not sure if this is what you are asking for though.