I assume you are referring to the USA.
Here's a report on human rights violations in the USA. It includes discussions about:
prison conditions the practices of solitary confinement (especially for the mentally ill and children), and even the death penalty, are violations of UN sanctioned human rights.
criminal justice the difference in sentencing and police treatment of minorities can be proven to be an inherent bias in the system - and therefore a violation of the right to be 'treated as an equal' and to have the right to a fair trial. This is not only a right from the UN Declaration, but is also repeated in Amendment 14 of the US constitution.
war on drugs the surveillance of drug dealers is often outside the right of an individual to privacy.
rights of non-citizens and migrants under the UN Declaration of Human Rights, all people have the same underlying right to healthcare, freedom to practice religion and freedom from discrimination on the basis of race.
torture during the 'War on Terror' various US groups have been accused of torturing militant personnel.
This is just a snap shot of a few of the 'most prevalent' or 'most routine' violations of human rights in the US. The Amnesty USA link (below) provides some focussed articles for further reading.
It is hard to come up with true violations of human rights in American schools. Perhaps the best one to cite would be bullying or harassment that is done because of a student's disability or sexuality or race or other such characteristic.
Within the US as a whole, there is again not much official governmental violation of human rights. If you believe a fetus is a life, then abortion is a violation of human rights. If you believe that gay marriage is a basic human right, then the denial of that in most states is also a violation of human rights.
When we start looking at other countries, human rights violations are much easier to spot. Muslim countries' punishment of apostasy, for example is a violation. So is China's denial of free speech rights.
The question posed is a deep thought provoking one. As a teacher in an elementary school I can say that some of the human rights are withheld from the children but only in order to facilitate their human right to a good education.
I have chosen some examples and commented on the, buses on information from this website. www.samaritanmag.com/we-have-30-basic-human-rights-do-you-know-them
1. We are all free and equal. This is an ideal that is strived towards in a school environment but it is not always feasible. Different children have different needs and as such need to be treated differently. Although not a negative in terms of what they are receiving during the school day it is an active way that a right is being denied.
9. No unfair detainment. One word. Detention. In the grand scheme of things detention after school is breaking this right. Every child across the many lands will declare that the detention given to them is unfair and in a sense they are right. No laws have been broken and in the eyes of the law and judiciary, nobody would be punished for the actions committed to land themselves in detention.
A very brief and simplistic way of looking at just a couple from an inside point of view. I hope it helps.
Violations of human rights in school may include the violations of freedom of speech, right to equality, same education and facilities, corporal punishment, bullying, etc.
One of the more famous cases of human rights violations in the US is the racial segregation of schools which was ended by desegregation starting with Little Rock Central High School, Arkansas. Desegregation was opposed heavily by people including the governor and the army had to be called in by President Eisenhower to ensure the entry of nine African-American students. Since then, the typical cases of human rights violations include bullying and corporal punishment.
Around the world, human rights violations are more commonly seen in dictatorial and communist countries. Differences of opinions, modern thoughts and free speech are not even tolerated in some parts of the world.