I've never heard of weekend detention. Good heavens!
I have faced this question myself, as a parent, with regards to after-school detention, and lunch detention.
In my state, New York, I found an official state education department document specifically about detention, which states:
After School Detention
To: School Administrators and Pupil Service
Personnel
From: Carl Friedman
Subject: After School Detention
Date: March 1996
The purpose of this field memorandum is to answer two questions. Can
a school district require students to stay after school for detention
as a disciplinary measure? Can the student be required to stay after
school when the student has other conflicting obligations, such as
caring for siblings or working?
Unfortunately, neither the law nor regulations directly address the
practice of detaining students after school as a method of discipline,
nor are there any precedential decisions. Education Law 1709(2)
provides the authority for boards of education to “establish such
rules and regulations concerning the order and discipline of the
schools.” Consequently, boards of education can maintain discipline
in the schools by reasonable means. Requiring a student to serve
detention at the end of a school day does not constitute an
unreasonable disciplinary practice per se. However, if a parent
objects to the imposition of after-school detention in a specific
situation, the district should impose an alternative means of
discipline, as there is no specific statutory authority for a school
to detain a student after the end of a regular school day against the
parents’ wishes.
As a final note, where a student is required to serve a period of
after-school detention and the student ordinarily receives
transportation, Education Law 3635 requires the district to transport
the student home after the detention period.
Last Updated: March 16, 2009
I looked at the North Carolina state education website and was not able to find anything there about detention. However, you could call and ask if there's something you've missed. You could also ask them the same question you posed here.
In addition, you should be able to download all of your district's local policies, and then search for the string "detention" within those documents. (I recommend File Locator Lite for efficient, effective searching.)
It is so much easier to advocate for your child when you cite local or state or federal policy or studies or reports.
Now I would like to mention some practical considerations, based on my experience.
If there might be a disability that could be contributing to either true behavioral issues, or issues that the school may be interpreting as a behavioral problem, you can ask that a Functional Behavioral Assessment be done. If the FBA is done properly, it can help turn the focus away from the child as the problem to a collaborative attempt to find ways to help the child be more successful in school.
The more you can learn about Positive Behavioral Interventions and Supports (PBIS) the better prepared you'll be when you meet with school staff. I looked at your state education department's website and found that although many individual districts in your state have PBIS materials on their websites, State Ed seems to have switched to a different approach and a different acronym, which I am not familiar with. Start here: https://www.dpi.nc.gov/districts-schools/districts-schools-support/integrated-academic-behavior-systems. The goal is to find state recommendations that you can print out and bring to a meeting, to ask politely about, e.g., "I've been reading about the multi-tiered system of support (MTSS) framework on the state education website. Has that framework been helpful for other students at our school who have faced behavioral challenges?" Maybe you can also pull out some specifics from those materials. The goal would be to show that you want to partner with the school, to help the student function more effectively in the classroom.
What I did, after a behavior incident which resulted in a detention, was to talk over the incident with my son, and help him understand how his actions might affect staff and other students, to try to stimulate an empathetic response from him. Once he "got" it, I asked him to write a short apology letter to the relevant staff and helped him send it. I asked him to explain in the letter why it wasn't fair to staff to have to see something disgusting, and why the incident could make some children not feel safe to come to school. (The incident involved him putting mucous, soap and water in a condom and leaving it on a bench in the gym locker room.) Then I wrote to the relevant staff and said that I felt that my son had now understood what was wrong with what he had done, and I felt that the process we had followed at home was a more effective way of applying positive discipline, than detention would be, and therefore I was requesting that the detention be waived.
I think that many schools give detention because they don't know what else to do. So, the best stance to take, in my opinion, is to share one's concern, show respect for their point of view, show that you want to partner with them to help the student be less disruptive (or whatever -- it depends on the situation), and then firmly state that you do not support detention for your child, stating the reason. (In my son's case, the reason was, detention simply brought out more oppositional and defiant behaviors -- the opposite of what we all wanted.)
From your question, I sense that you are wondering if there's anything to be afraid of, in terms of legal actions toward the parents. In my experience, there are three ways schools lash out when they don't know what else to do:
(a) If the relationship deteriorates and gets very bad, the school may send a letter stating that the parent may no longer enter school property. If this happens, it is important to follow the instructions to the letter. If not, the parent could be arrested. This type of letter is becoming more and more common. To avoid getting such a letter, it can be helpful to always keep one's cool in meetings and emails. (Even so, I have seen districts make up "violent" parental behaviors out of whole cloth....)
(b) Sometimes a school will report a parent to Child Protective Services, exaggerating a real problem or making one up. If this happens, it is helpful to try to keep one's cool, and patiently go through the investigative process. Once the parent has been exonerated, then one can, for example, file a complaint about retaliation for advocacy for the child.
(c) Sometimes school staff will take out their frustrations on the child, with the result that the child feels bullied by staff, loses self-esteem, loses sleep, loses motivation to learn, loses motivation to attend school, etc. This can be a really tough problem to solve when it happens. In such cases it can be helpful to bring an advocate along to school meetings, to help everybody listen better, and look at the situation in more constructive ways.
I have heard of one parent who brought a state trooper with her when she went to take her child home. It worked in her case. It might not work for you. And even if it works, it might turn a not-great relationship with the school even more sour.
You could also ask your question of COPAA, the Council of Parent Attorneys and Advocates for a legal answer to the question, both for your state, and in general.