You have 2 options available to you:
1. Remove the content from your website and settle the matter.
2. Send a reply in the form of a legal notice stating the content which is being claimed to be infringing their copyright is of common knowledge and general in nature and that the same does not amount to a copyright infringement. Thereafter, they shall have the option of filing a complaint in the Court as copyright infringement is a criminal offence and if the same is proven then the minimum punishment is 6 months imprisonment or a fine of Rs 50,000/-. You shall have the right to defend yourself and prove that the content does not amount to copyright and therefore, cannot be claimed to be a copyright of the School. You can also show that you are the prior user of this name.