eng grammer correction

Grammatical errors:
if punishment is not useful.
You must start every sentence with a capital letter. This is part of a conditional sentence, you cannot use full stop here. So, it should be rewritten as:
If punishment is not useful,
The last resort maybe have to talk to their parent.
You should use a different subject such as "the school" or "the teacher" because they are the ones who can talk.
the school may have to talk to the students' parents as the last resort.
It need parents co-ordinated response with school
"The school" should be the subject of this sentence.
"co-ordinated response" - Do you mean "cooperation"?
The school needs the cooperation of the parents.
This is more advisable to eliminate students behaviour.
"advisable " means something recommendable. According to the contextual meaning, "effective " may be a better word.
"behaviour " should be "misbehaviour "
This is more effective to eliminate the students' misbehaviour.

So, this is the corrected piece:

If punishment is not useful, the school may have to talk to the students' parents as the last resort. The school needs the cooperation of the parents. This is more effective to eliminate the students' misbehaviour.

To enhance fluency, I suggest rewriting the sentences as follows:

For students who are not deterred by punishment, the school may have to talk with their parents or guardians to find out the culprit and try to solve the problem together. This is more effective in eliminating the students' misbehaviour.

If punishment is of no use, then the alternative maybe we need to talk to their parents. School needs parents co-operation to eliminate students bad behavior.

parent = single parent (father or mother only)
parents = father & mother

whether writing short sentence or long essay it is equally important that they make sense individually.