How to correct our mistakes in our writings

Dear students,

I have realize that many of you have not corrected the mistakes you made in your compositions that have been already corrected. I will explain this again to be sure you understand what you have to do.
Whenever you see an underlined word or a sentence you have to correct below the test. You will see something written under the line to tell you what kind of mistake it is.
These are the types of mistake you will see:
G: Grammar mistake
T: You have used a wrong tense
O: Change the order of the words
S: Check your spelling
?: I don't understand the meaning

It is important that you correct them and show them to me, to be sure that you learn how to write it.