diff --git a/models/br_inep_saeb/br_inep_saeb__aluno_ef_9ano.sql b/models/br_inep_saeb/br_inep_saeb__aluno_ef_9ano.sql
index fa9578c8..efc96599 100644
--- a/models/br_inep_saeb/br_inep_saeb__aluno_ef_9ano.sql
+++ b/models/br_inep_saeb/br_inep_saeb__aluno_ef_9ano.sql
@@ -13,7 +13,6 @@
     )
 }}
 
-
 select
     safe_cast(ano as int64) ano,
     safe_cast(sigla_uf as string) sigla_uf,
diff --git a/models/br_inep_saeb/code/fix_microdados_aluno_ef_9ano_2021.py b/models/br_inep_saeb/code/fix_microdados_aluno_ef_9ano_2021.py
new file mode 100644
index 00000000..be89e273
--- /dev/null
+++ b/models/br_inep_saeb/code/fix_microdados_aluno_ef_9ano_2021.py
@@ -0,0 +1,227 @@
+import polars as pl
+import os
+import basedosdados as bd
+from databasers_utils import TableArchitecture
+import zipfile
+
+ROOT = os.path.join("models", "br_inep_saeb")
+INPUT = os.path.join(ROOT, "input")
+TMP = os.path.join(ROOT, "tmp")
+OUTPUT = os.path.join(ROOT, "output", "aluno_ef_9ano")
+
+ZIP_URL = "https://download.inep.gov.br/microdados/microdados_saeb_2021_ensino_fundamental_e_medio.zip"
+
+ZIP_FILE = os.path.join(INPUT, os.path.basename(ZIP_URL))
+
+os.system(
+    f"wget {ZIP_URL} --no-check-certificate -o {INPUT}/{os.path.basename(ZIP_URL)}"
+)
+
+with zipfile.ZipFile(ZIP_FILE) as z:
+    print(z.namelist())
+
+with zipfile.ZipFile(ZIP_FILE) as z:
+    z.extract("DADOS/TS_ALUNO_9EF.csv", TMP)
+
+# Apenas Roraima (RR)
+df = pl.read_csv(os.path.join(TMP, "DADOS/TS_ALUNO_9EF.csv"), separator=";").filter(
+    pl.col("ID_UF") == 14
+)
+
+csv_columns = df.columns
+
+arch = TableArchitecture(
+    "br_inep_saeb",
+    {
+        "aluno_ef_9ano": "https://docs.google.com/spreadsheets/d/1KLkvX8z9AKIe4iM5EeahVBCVUjikNvHJWfT-qTjM2IU/edit?gid=0#gid=0",
+    },
+)
+
+tables_arch = arch.tables()
+
+arch_ef_9ano = tables_arch["aluno_ef_9ano"]
+
+cols_disciplina = [
+    i
+    for i in csv_columns
+    if i.endswith("LP") or i.endswith("MT") or i.endswith("CH") or i.endswith("CN")
+]
+
+index_cols = [
+    "ID_SAEB",
+    "ID_REGIAO",
+    "ID_UF",
+    "ID_MUNICIPIO",
+    "ID_AREA",
+    "ID_ESCOLA",
+    "IN_PUBLICA",
+    "ID_LOCALIZACAO",
+    "ID_TURMA",
+    "ID_SERIE",
+    "ID_ALUNO",
+    "IN_SITUACAO_CENSO",
+    "IN_AMOSTRA",
+    "ESTRATO",
+    "IN_PREENCHIMENTO_QUESTIONARIO",
+    "IN_INSE",
+    "INSE_ALUNO",
+    "NU_TIPO_NIVEL_INSE",
+    "PESO_ALUNO_INSE",
+]
+
+on = [
+    "PROFICIENCIA_LP_SAEB",
+    "PROFICIENCIA_MT_SAEB",
+    "PROFICIENCIA_CH_SAEB",
+    "PROFICIENCIA_CN_SAEB",
+    "ERRO_PADRAO_LP_SAEB",
+    "ERRO_PADRAO_MT_SAEB",
+    "ERRO_PADRAO_CH_SAEB",
+    "ERRO_PADRAO_CN_SAEB",
+    *cols_disciplina,
+]
+
+
+def find_disc(value: str) -> str:
+    """
+    Returns two characters identifying the subject from a variable
+
+    Parameters
+    ----------
+    value
+        Variable name
+
+    Examples
+    --------
+    >>> find_disc("PROFICIENCIA_CH_SAEB")
+    >>> "CH"
+    """
+    last_two_char = value[-2:]
+    if last_two_char not in ["LP", "MT", "CH", "CN"]:
+        return value.split("_")[-2]
+    return last_two_char
+
+
+def renames_variables(value: tuple[str, str]) -> str:
+    """
+    Rename variables using subject
+
+    Parameters
+    ----------
+    value:
+        Tuple (two values), lhs is variable name and rhs is subject
+
+    Examples
+    --------
+    >>> renames_variables(("PROFICIENCIA_CH_SAEB", "CH"))
+    >>> "PROFICIENCIA__SAEB"
+    """
+    variable, disc = value
+    parts = variable.split("_")
+
+    if disc in parts:
+        return "_".join([i for i in parts if i not in disc])
+
+    return variable
+
+
+other_index_cols = [
+    i
+    for i in csv_columns
+    if i.startswith("TX_RESP") and i.split("_")[-1] not in ["LP", "MT", "CH", "CN"]
+]
+
+
+def wide_to_long(df: pl.DataFrame) -> pl.DataFrame:
+    """
+    Convert a DataFrame from wide to long format
+    """
+    return (
+        df.unpivot(on=on, index=[*index_cols, *other_index_cols])
+        .with_columns(
+            pl.col("variable")
+            .map_elements(lambda v: find_disc(v), return_dtype=pl.String)
+            .alias("disciplina"),
+        )
+        .with_columns(
+            pl.struct(["variable", "disciplina"]).map_elements(
+                lambda cols: renames_variables((cols["variable"], cols["disciplina"])),
+                return_dtype=pl.String,
+            )
+        )
+        .pivot(
+            on="variable",
+            values="value",
+            index=[*index_cols, *other_index_cols, "disciplina"],
+        )
+    )
+
+
+manual_renames = {
+    "PROFICIENCIA_SAEB": "proficiencia_saeb",
+    "ERRO_PADRAO_SAEB": "erro_padrao_saeb",
+    "IN_PREENCHIMENTO": "preenchimento_caderno",
+    "IN_PRESENCA": "presenca",
+    "ID_CADERNO": "caderno",
+    "ID_BLOCO_1": "bloco_1",
+    "ID_BLOCO_2": "bloco_2",
+    "ID_BLOCO_3": "bloco_3",
+    "NU_BLOCO_1_ABERTA": "bloco_1_aberto",
+    "NU_BLOCO_2_ABERTA": "bloco_2_aberto",
+    "TX_RESP_BLOCO1": "respostas_bloco_1",
+    "TX_RESP_BLOCO2": "respostas_bloco_2",
+    "TX_RESP_BLOCO3": "respostas_bloco_3",
+    "CO_CONCEITO_Q1": "conceito_q1",
+    "CO_CONCEITO_Q2": "conceito_q2",
+    "IN_PROFICIENCIA": "indicador_proficiencia",
+    "PESO_ALUNO": "peso_aluno",
+    "PROFICIENCIA": "proficiencia",
+    "ERRO_PADRAO": "erro_padrao",
+}
+
+tb_aluno_ef_9ano = bd.Table("br_inep_saeb", table_id="aluno_ef_9ano")
+
+bq_cols = tb_aluno_ef_9ano._get_columns_from_bq()
+
+cols_dict = dict([(i["name"], i["type"]) for i in bq_cols["columns"]])
+
+common_renames = {
+    i["original_name_2021"]: i["name"]
+    for i in arch_ef_9ano.loc[arch_ef_9ano["original_name_2021"] != ""][
+        ["name", "original_name_2021"]
+    ].to_dict("records")
+    if i["original_name_2021"] in csv_columns
+}
+
+df = (
+    wide_to_long(df)
+    .rename({**common_renames, **manual_renames})
+    .with_columns(pl.lit("RR").alias("sigla_uf"))
+    .drop(["ID_UF"])
+)
+
+
+empty_cols_to_add = [i for i in cols_dict.keys() if i not in df.columns]
+
+len(empty_cols_to_add)
+
+df = (
+    df.with_columns([pl.lit(None).alias(col) for col in empty_cols_to_add])
+    .with_columns([pl.col(col_name).cast(pl.String) for col_name in cols_dict.keys()])
+    .select(*cols_dict.keys())
+    .filter(pl.col("disciplina") == "MT")
+)
+
+assert len(df.columns) == len(bq_cols["columns"])
+
+PARTITION_DIR = os.path.join(OUTPUT, "ano=2021", "sigla_uf=RR")
+
+os.makedirs(PARTITION_DIR, exist_ok=True)
+
+df.write_csv(os.path.join(PARTITION_DIR, "microdados_mt.csv"))
+
+tb_aluno_ef_9ano.create(
+    OUTPUT,
+    if_table_exists="replace",
+    if_storage_data_exists="replace",
+)
diff --git a/poetry.lock b/poetry.lock
index add9d438..9d41df00 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1863,6 +1863,47 @@ files = [
 docs = ["furo (>=2023.7.26)", "proselint (>=0.13)", "sphinx (>=7.1.1)", "sphinx-autodoc-typehints (>=1.24)"]
 test = ["appdirs (==1.4.4)", "covdefaults (>=2.3)", "pytest (>=7.4)", "pytest-cov (>=4.1)", "pytest-mock (>=3.11.1)"]
 
+[[package]]
+name = "polars"
+version = "1.7.0"
+description = "Blazingly fast DataFrame library"
+optional = false
+python-versions = ">=3.8"
+files = [
+    {file = "polars-1.7.0-cp38-abi3-macosx_10_12_x86_64.whl", hash = "sha256:515201ae296a3ef770102dab196f207581b617c7a053cf200aff57fdca03001f"},
+    {file = "polars-1.7.0-cp38-abi3-macosx_11_0_arm64.whl", hash = "sha256:5c7b03a60b3490f7ca17e0a69208b29bea1a70f62b394443035f196c751ca126"},
+    {file = "polars-1.7.0-cp38-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:56042ca1e35c2e6a08e2f37d981a46af685e273cde08944328921a22ed5e1926"},
+    {file = "polars-1.7.0-cp38-abi3-manylinux_2_24_aarch64.whl", hash = "sha256:bdb11cc9807d3886a8ea516a9d829fb9d8570d11b80be9310f825d1331011dbd"},
+    {file = "polars-1.7.0-cp38-abi3-win_amd64.whl", hash = "sha256:3d0fe4b8505c918114bbef6c8f8bd7a245ce3b7cd59f3c9fba2c9cd1f24606f9"},
+    {file = "polars-1.7.0.tar.gz", hash = "sha256:cd90892c8ed0ee755fdf0a0ebc08489c6f0094eaa7eed5edb48956c3e431ef8c"},
+]
+
+[package.extras]
+adbc = ["adbc-driver-manager[dbapi]", "adbc-driver-sqlite[dbapi]"]
+all = ["polars[async,cloudpickle,database,deltalake,excel,fsspec,graph,iceberg,numpy,pandas,plot,pyarrow,pydantic,style,timezone]"]
+async = ["gevent"]
+calamine = ["fastexcel (>=0.9)"]
+cloudpickle = ["cloudpickle"]
+connectorx = ["connectorx (>=0.3.2)"]
+database = ["nest-asyncio", "polars[adbc,connectorx,sqlalchemy]"]
+deltalake = ["deltalake (>=0.15.0)"]
+excel = ["polars[calamine,openpyxl,xlsx2csv,xlsxwriter]"]
+fsspec = ["fsspec"]
+gpu = ["cudf-polars-cu12"]
+graph = ["matplotlib"]
+iceberg = ["pyiceberg (>=0.5.0)"]
+numpy = ["numpy (>=1.16.0)"]
+openpyxl = ["openpyxl (>=3.0.0)"]
+pandas = ["pandas", "polars[pyarrow]"]
+plot = ["altair (>=5.4.0)"]
+pyarrow = ["pyarrow (>=7.0.0)"]
+pydantic = ["pydantic"]
+sqlalchemy = ["polars[pandas]", "sqlalchemy"]
+style = ["great-tables (>=0.8.0)"]
+timezone = ["backports-zoneinfo", "tzdata"]
+xlsx2csv = ["xlsx2csv (>=0.8.0)"]
+xlsxwriter = ["xlsxwriter"]
+
 [[package]]
 name = "pre-commit"
 version = "3.8.0"
@@ -2872,4 +2913,4 @@ type = ["pytest-mypy"]
 [metadata]
 lock-version = "2.0"
 python-versions = "~3.9"
-content-hash = "449d554196de70d2bc05c8e9a343e3cfd2ccbadaf913590818f0ed8d27e8fef3"
+content-hash = "98e3b8ca5ac1d40be1d09241e907e7e1bc99e54cf66e550091591fad6dabbdb3"
diff --git a/pyproject.toml b/pyproject.toml
index 03e3ca5f..cc7e8ec0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,3 +29,4 @@ markdown = "^3.3.6"
 basedosdados = {version = "2.0.0b16", extras = ["upload"]}
 gql = "^3.5.0"
 databasers-utils = {git = "https://github.com/basedosdados/databasers-utils.git#main"}
+polars = "^1.7.0"