34 CFR § 303.7 - Consent.
Consent means that—
(a) The parent has been fully informed of all information relevant to the activity for which consent is sought, in the parent's native language, as defined in § 303.25;
(b) The parent understands and agrees in writing to the carrying out of the activity for which the parent's consent is sought, and the consent form describes that activity and lists the early intervention records (if any) that will be released and to whom they will be released; and
(c)
(1) The parent understands that the granting of consent is voluntary on the part of the parent and may be revoked at any time.
(2) If a parent revokes consent, that revocation is not retroactive (i.e., it does not apply to an action that occurred before the consent was revoked).