set heading on

SPOOL U:\...\tt.txt

ttitle  left " Test report "  skip 1 

COLUMN A HEADING 'Last Name' format a35
column b heading 'First Name' format a35
column c heading 'Stu #' format 999999
column d heading 'Grade' format 99

select last_name A, first_name B, student_number C, grade_level D
from students where 
schoolid = 999 
and enroll_status = 0 
and rownum <= 15; 

spool off
set heading off

I dont know what you mean....it looks ok to me.

I edited your script and saved as c:\temp\test.sql

set heading on

SPOOL c:\temp\text.txt

ttitle  left " Test report "  skip 1 

COLUMN A HEADING 'Last Name' format a35
column b heading 'First Name' format a35
column c heading 'Stu #' format 999999
column d heading 'Grade' format 99

select owner A, object_name B, object_type C
from all_Objects
where rownum <= 15; 

spool off
set heading off

Then I ran it

SQL> @c:\temp\test.sql

 Test report
Last Name                           First Name                          Stu #
----------------------------------- ----------------------------------- -----------
SYS                                 I_COBJ#                             INDEX
SYS                                 I_USER2                             INDEX
SYS                                 CCOL$                               TABLE
SYS                                 I_COL2                              INDEX
SYS                                 FILE$                               TABLE
SYS                                 C_OBJ#                              CLUSTER
SYS                                 C_COBJ#                             CLUSTER
SYS                                 I_TS1                               INDEX
SYS                                 C_USER#                             CLUSTER
SYS                                 CLU$                                TABLE
SYS                                 C_TS#                               CLUSTER
SYS                                 I_COL1                              INDEX
SYS                                 I_OBJ5                              INDEX
SYS                                 I_CDEF3                             INDEX
SYS                                 I_CDEF2                             INDEX

15 rows selected.

and my spool file looked like this

 Test report
Last Name                           First Name                          Stu #
----------------------------------- ----------------------------------- -----------------------
SYS                                 I_COBJ#                             INDEX
SYS                                 I_USER2                             INDEX
SYS                                 CCOL$                               TABLE
SYS                                 I_COL2                              INDEX
SYS                                 FILE$                               TABLE
SYS                                 C_OBJ#                              CLUSTER
SYS                                 C_COBJ#                             CLUSTER
SYS                                 I_TS1                               INDEX
SYS                                 C_USER#                             CLUSTER
SYS                                 CLU$                                TABLE
SYS                                 C_TS#                               CLUSTER
SYS                                 I_COL1                              INDEX
SYS                                 I_OBJ5                              INDEX
SYS                                 I_CDEF3                             INDEX
SYS                                 I_CDEF2                             INDEX

15 rows selected.