Simple question about schema (is this supposed to happen?)
I would confirm that you are connecting using the correct login, and that you have not incorrectly assigned some other permission.

I executed the script that you provided above, and then used execute as to test the select permissions and received SELECT permission denied errors for both (as I would expect).

Adjusted comments slightly, but the following I received what I expected (SQL Server 2012)

/* Create new database */
CREATE database dba_schema
GO

use dba_schema 
GO

/* Create new table in dbo schema */
CREATE TABLE dbo.tabela1 ( id int ) 
GO

/* Add new login */  
USE [master]
GO
CREATE LOGIN [schema_user] WITH PASSWORD=N'schema_user', 
DEFAULT_DATABASE=[dba_schema], CHECK_EXPIRATION=OFF, CHECK_POLICY=OFF
GO

/* Add new user */
USE [dba_schema]
GO
CREATE USER [schema_user] FOR LOGIN [schema_user]
GO

/* Set default schema for user */
USE [dba_schema]
GO
ALTER USER [schema_user] WITH DEFAULT_SCHEMA=[dbo]
GO

/* Create new schema */
CREATE SCHEMA schema1
GO

/* Add new table to new schema */
CREATE TABLE schema1.tabela1 ( id int ) 
GO

/* Impersonate the new login of schema_user and query the tables */
EXECUTE AS LOGIN = 'schema_user';
/* Confirm we've impersonated correctly */
SELECT SUSER_NAME();
/* Run the selects */
SELECT * FROM dbo.tabela1;
SELECT * FROM schema1.tabela1;
REVERT;