shcool_id    year    students

  100001      1        80
  100001      2        98
  100002      1        71

shcool_id         name

    100001         SCHOOL_A
    100002         SCHOOL_B
    100003         SCHOOL_C

dict = {}
    for i in range(escolas.shape[0]):
        dict[escolas.iloc[i,0]] = escolas.iloc[i,1]

escolas["scholl_id"] = escolas["scholl_id"].replace(dict)

df1['shcool_id'].map(df2.set_index('shcool_id')['name'])

0    SCHOOL_A
1    SCHOOL_A
2    SCHOOL_B

df1['shcool_id']=df1['shcool_id'].map(df2.set_index('shcool_id')['name'])
print(df1)

  shcool_id  year  students
0  SCHOOL_A  1     80
1  SCHOOL_A  2     98
2  SCHOOL_B  1     71