It doesn't appear that you lawfully can do this as you would not be a party to the recording:
An individual can record or disclose wire, oral, or electronic communications to which he is a party, or if one party to the communication consents. Otherwise, it is a felony. Va. Code Ann. § 19.2-62.
A lawyer’s recording of a telephone conversation with the consent of one, but not all, parties to the conversation was found to be legal, though unethical, under Virginia law. U.S. v. Smallwood, 365 F.Supp.2d 689 (2005).
Under the statute, consent is not required for the taping of a non-electronic communication uttered by a person who does not have a reasonable expectation of privacy in that communication. See definition of “oral communication,” Va. Code Ann. § 19.2-61; Belmer v. Commonwealth, 553 S.E.2d 123 (Va. App. 2001).
Criminal penalties for violating the law include imprisonment for one to five years or, at the discretion of a jury or judge, confinement in jail for up to 12 months and a fine of not more than $2,500, either or both. Va. Legis. 579. A civil cause of action is authorized by statute for $100 per day of violation or $1,000, whichever is greater. Va. Code Ann. § 19.2-69. Punitive damages, attorney fees, and litigation costs can be recovered under the statute as well. Va. Code Ann. § 19.2-69.
Besides, even if this were lawful in your State, that doesn't mean school administration won't summarily dismiss you when they find out you've made a video recording. Why not just go to the principal with your concerns and let him or her handle it?
A person, who is nice to you, but rude to a waiter, is not a nice person. (This is very important. Pay attention. It never fails.)