Hi Colin!
Thanks for your tips. 
With help of Rails Guides on ActiveRecord Associations I reach this
point:
= Migrations =
class CreateSchools < ActiveRecord::Migration
def change
create_table :schools do |t|
t.string :name
t.timestamps
end
end
end
class CreateTeams < ActiveRecord::Migration
def change
create_table :teams do |t|
t.integer :school_id
t.string :name
t.timestamps
end
end
end
class CreatePeople < ActiveRecord::Migration
def change
create_table :people do |t|
t.string :name
t.timestamps
end
end
end
class CreateTeachers < ActiveRecord::Migration
def change
create_table :teachers, :id => false do |t|
t.integer :team_id
t.integer :person_id
end
add_index :teachers, [:team_id, :person_id]
end
end
class CreateStudents < ActiveRecord::Migration
def change
create_table :students, :id => false do |t|
t.integer :team_id
t.integer :person_id
end
add_index :students, [:team_id, :person_id]
end
end
= Models =
class School < ActiveRecord::Base
has_many :teams
end
class Team < ActiveRecord::Base
belongs_to :school
has_many :teachers
has_many :people, :through => :teachers
has_many :students
has_many :people, :through => :students
end
class Person < ActiveRecord::Base
end
class Teacher < ActiveRecord::Base
belongs_to :team
belongs_to :person
end
class Student < ActiveRecord::Base
belongs_to :team
belongs_to :person
end
===
But after put some test data into the tables I cannot get, for
example, the names os the students of some team or what are the teachers
that taught some team.
Look what I tried:
samsara:first_app leandro$ rails console
Loading development environment (Rails 4.0.0.beta1)
2.0.0-p0 :001 > team = Team.find_by_name(“Turma 2A”)
Team Load (0.9ms) SELECT “teams”.* FROM “teams” WHERE “teams”.“name”
= ‘Turma 2A’ LIMIT 1
=> #<Team id: 4, school_id: 4, name: “Turma 2A”, created_at:
“2013-04-19 12:42:47”, updated_at: “2013-04-19 12:42:47”>
2.0.0-p0 :002 > team.teachers
Teacher Load (1.6ms) SELECT “teachers”.* FROM “teachers” WHERE
“teachers”.“team_id” = ? [[“team_id”, 4]]
=> #<ActiveRecord::Associations::CollectionProxy [#<Teacher team_id: 4,
person_id: 2>, #<Teacher team_id: 4, person_id: 15>]>
2.0.0-p0 :003 > team.students
Student Load (0.2ms) SELECT “students”.* FROM “students” WHERE
“students”.“team_id” = ? [[“team_id”, 4]]
=> #<ActiveRecord::Associations::CollectionProxy [#<Student team_id: 4,
person_id: 8>, #<Student team_id: 4, person_id: 9>, #<Student team_id:
4, person_id: 11>, #<Student team_id: 4, person_id: 12>]>
2.0.0-p0 :004 >
I would like to get the People objects instead of the intermediate
associative tables “teachers” and “students”. 
Best regards,
Mosoleu
Colin L. wrote in post #1106292:
On 19 April 2013 14:45, Leandro P. [email protected] wrote:
The details are not correct as I have not looked at the ER diagram,
and it is arguable whether you should start with such a diagram in the
first place, but in order to understand the basics of what rails can
do for you I suggest you work right through a good tutorial such as
railstutorial.org, which is free to use online. Also look at the
Rails Guides, particularly ActiveRecord Associations.
Colin
