Do not sign a broad authority document just because it is framed as "for emergencies"
If you just turned 18, your parent no longer has automatic control over your medical information, school records, or other adult decisions just because they are your parent. If a document truly is only for emergencies, it should say that clearly and narrowly. If it also grants ongoing access to records, financial authority, education authority, or general life-decision authority, then it is more than an emergency form.
The clearest official source on school records is FERPA. The U.S. Department of Education says: "When a student becomes an eligible student, the rights accorded to, and consent required of, parents under this part transfer from the parents to the student." It defines an "eligible student" as one who "has reached 18 years of age or is attending an institution of postsecondary education." Source: https://studentprivacy.ed.gov/ferpa
For health privacy, university and hospital guidance lines up the same way. James Madison University tells families: "Once a student turns 18, HIPAA turns control of their health care and records over to them." Source: https://www.jmu.edu/family/resources/student-privacy.shtml
Nationwide Children's says: "When your child turns 18, they become a legal adult. This means that they are now fully responsible for their medical care decisions, and their doctors and nurses can talk only to them." Source: https://www.nationwidechildrens.org/family-resources-education/700childrens/2022/05/balancing-independence-and-support-for-young-adults
A true emergency-only health care power of attorney is usually about decision-making if you cannot speak for yourself. Ohio State Student Legal Services describes a healthcare power of attorney this way: it "authorizes trusted individual(s) to make medical decisions if your student is unable to make them for themselves." That is consistent with the "emergency" framing.
But the same Ohio State page also warns that the form may go further. It says the healthcare power of attorney can contain language that, "if initialed by the student would allow for their agent to obtain protected health care information immediately and at any future time. This means that agents can obtain this information, even if it is not an emergency." Source: https://studentlegal.osu.edu/hpoa
That is the key red flag in your situation: some forms combine emergency authority with non-emergency access. If the paper covers "a lot more than that," your reading may be exactly right.
LawHelpNY explains that a power of attorney can be "very broad or very limited powers." Its examples of powers include "real estate transactions," "banking transactions," "claims and litigation," "making gifts of up to $500 in a calendar year," and "health care billing and payment matters, records, reports and statements." It also warns: "Your agent will have a great amount of power over some of your most personal affairs." Source: https://www.lawhelpny.org/resource/power-of-attorney-2
That matters because "for emergencies" is a description, not a legal limit. The legal limit is whatever the document actually authorizes.
Nationwide Children's lays out less-invasive options:
Same source: https://www.nationwidechildrens.org/family-resources-education/700childrens/2022/05/balancing-independence-and-support-for-young-adults
Ohio State Student Legal Services also separates these documents instead of treating them as one package. It lists a healthcare power of attorney, HIPAA release, FERPA release, living will, and financial power of attorney as distinct tools. Source: https://studentlegal.osu.edu/hpoa
That means you do not have to accept an all-or-nothing bundle if what you actually want is limited emergency access.
603 Legal Aid gives direct consumer guidance: "Do not sign a contract under pressure." It also notes that "Generally speaking, once you sign a contract, you are obligated," and that there is no general 3-day cooling-off period in New Hampshire. Source: https://www.603legalaid.org/preventive-measures
That page is consumer-contract guidance rather than a state-specific POA rule, but the practical lesson fits your situation: if someone is pushing you to sign immediately, that is a reason to stop and get the document explained first.
Revocation is often possible, but it is extra work and may not instantly undo everything in practice. The New York City Bar says: "You can revoke your power of attorney at any time and for any reason, as long as you are mentally able." It also says the revocation "must be in writing" and that you must inform "banks and other institutions" plus the agent. Source: https://www.nycbar.org/get-legal-help/article/wills-trusts-and-elder-law/power-attorney/ending-your-power-of-attorney/
Washington Law Help gives the same basic rule in simpler form: "You can cancel (revoke) your power of attorney at any time by giving a written notice to your agent." Source: https://www.washingtonlawhelp.org/en/cancel-revoke-power-attorney
So the document is not necessarily permanent, but that is not a good reason to sign something unclear. It is easier to refuse now than to unwind later.
Based on the sources, the strongest conclusions are:
Power-of-attorney wording and revocation rules vary by state. The core pattern is consistent across the sources above, but the exact effect of the document depends on your state's form and the language on the page you were asked to sign.