Getting into an ivy league school?

Harvard, and most universities, want your unweighted cumulative gpa at the end of junior year to apply.
Their acceptance rate is under 6%. This year they had 43,749 applications. Many of those students applying will have a 4.0 unweighted cumulative gpa. It takes more than a great gpa to get in. You need awards, leadership positions in what ever you do. To have done something outstanding, unique.
Harvard has closed applications for the fall 2019 school year. For the 2020 school year applications deadline dates are in November 2019. Before you get your senior first semester grades. You will need to send in your senior grades, your acceptance is contingent on the them.

You're on the right track, but obtaining a high GPA isn't everything. How's your SAT/ACT scores? Have you taken any AP classes in your high school? Remember, to get into any Ivy League school, you're completing with other advanced students who are over-achievers. You cannot stand a chance without working/studying extremely hard. You have to achieve something really incredible, like becoming an AP Scholar, or winning an international award for something, or playing a sport in your high school. Just obtaining a high GPA alone isn't enough. You have to excel at everything you do.

Even getting a 4.0 all though high school is no guarantee of getting into Harvard or any other elite university. About 95% of ALL applicants are rejected from Harvard -- even if they have perfect GPAs and scores. Also, law is a graduate degree and you don't need to attend Harvard undergrad to get into Harvard Law.

SO...
It is time that you start using a website like Niche or BigFuture to look at what schools are a good fit for your academically and discuss what your family can afford.

Exceptional schools only want exceptional people. A straight 4.0 GPA for all 4 years is nowhere near enough to be considered by any university of the caliber of Harvard, Stanford, etc. All the applicants have that, and only 5-6% of them might be accepted. What have you accomplished which is extraordinary?

BTW, you need to earn a 4-year bachelor's degree from a superior school, with about a 4.0 GPA before you can apply to law school. You will need exceptional achievements throughout college as well as high school. Do you have that?

You do not mention your SAT scores, but it would be very hard to get into Harvard with a GPA of 3.8. In typical years, Ivy League schools receive between 25,000 and 35,000 applications. Of those, 10,000 to 15,000 are exceptionally well qualified applicants. They are competing for about 2,000 spots.

As mentioned in other answers, one must first have a 4 year college degree to go to law school.

law is a graduate school. they take applications from many people with undergrad degrees for other universities.

you should probably try to raise your average as much as possible now and through next year, then go to a first class undergraduate school [that Harvard Law thinks well of].

How to know that last bit? ask them!

Harvard law or Harvard undergrad--you say both. Is that enough to guarantee entrance into Harvard? No not even a 4.0 is enough. as almost everyone who applies can claim that. You need all kinds of things that would set you apart. Consider a cheaper undergrad and save the $ for law school.