Database, SQL database

Question

I am doing a job for the college whose goal is to create a table using Oracle Live SQL

So far mine’s been like this:

create table ALUNO (   
  rgm      number(8),   
  nome          varchar2(50),   
  nome_pai      varchar2(50), 
  nome_mae      varchar2(50),
  dt_nascimento date,
  id_sexo       varchar(1),
  constraint pk_aluno primary key (rgm)   
);

create table MATRICULA (   
  rgm        number(8),
  cd_classe  number(8), 
  matricula date,
  constraint pk_matricula primary key (rgm), 
  constraint fk_matricula foreign key (cd_classe),
  references ALUNO (rgm)  
);

create table CLASSE (
cd_classe number(8),
Nr_anoLetivo number(4),
Nr_serie number(2),
Sg_turma varchar2(2),
Cd_escola number(6),
Cd_grau number(2),
Cd_periodo number(2),
Constraint pk_matricula primary key (cd_classe)
);

but I’m not sure if it’s right. If you can direct me to correct what’s missing or what’s wrong, I’ll be grateful!