But is this happening?
The OP’s description suggests that she fixes the errors, and the students takes the paper back and incorporates the corrections. Is the OP actually explaining anything? Is the OP helping the student to improve her writing, or is she making sure that the student has no incentive to improve her writing because someone will be there to fix the mistakes?
When i correct my students’ writing, it is done with a view to encouraging them to improve. For example, if i find that the student has a problem with writing sentence fragments, or with subject/verb agreement, or with dangling modifiers, i mark the error, and link to an explanation, usually on the Purdue University Online Writing Lab website, which is an excellent resource.
This is made easier by the fact that my students submit their papers electronically, and i return them the same way. Thus it is a simple matter for me to insert a URL link for the student to follow.
So, in the cases described above, the student will see part of their sentence highlighted, with a comment that says something like:
Sentence fragment
https://owl.english.purdue.edu/owl/resource/620/1/
Subject/verb agreement
https://owl.english.purdue.edu/owl/resource/599/01/
Dangling modifier
https://owl.english.purdue.edu/owl/resource/597/1/
This lets them know the name of the problem, and gives them a resource that will help them identify and fix the problem.
At the end of their papers, students with writing problems will also see, as part of my overall comments, a paragraph that looks something like this:
Your essay contains some problems related to grammar and sentence construction. I have identified some examples in your paper, and have provided links to resources that will help you identify and correct the problems. If you would like further assistance with your writing, you should consider contacting the Writing Center on campus. I would also be happy to help you with your writing, and to explain these concepts in more detail, if you visit me during my office hours.
This sort of thing needs to involve some effort on their part. I’m not simply going to correct the mistakes, and i also make clear to the students that i take their writing into account when evaluating their papers and assigning a grade. If the first paper a student submits has some problems, i will point them out, provide resources, and offer help. If, as the semester progresses, that same student continues to make exactly the same mistakes, and seems to have made little or no effort to improve his or her writing, then the grades the student receives for written work will suffer a bit.