If you have not started college yet, I am not sure that you need to decide before you go. Getting a bachelor's degree takes four years. The first two years are often just core subjects, without a need to really know your major. I would recommend that you take those two years to take classes on teaching, theater, and initial classes on taking care of animals. This is the time for you to work through your expectations on each role. All of them are challenging in their own way. Your challenge is to determine which one you would want to still do even when it gets hard, or especially when it gets hard.
Additionally, like others have mentioned, I would seek out professionals in each field and gather advice/input as to what they love about the career and what they would like to to change about the career.
It’s alright to not know everything right now either. I, myself, struggled with choosing the right career path. But all in good time, you’ll discover what it is that you’ll love to do.
Depending on where you are in your education, you most likely don't need to rush it, just take your time. Nobody can rush you, if anything you can take a small break to decide what you want to do.
I would do some research on what it really means to be an actor, teacher, or lawyer and try to make a pros and cons list. This might help you start thinking about the careers and what your life could look like. I don't think you need to decide right away, but start thinking about them. Also, I would encourage you to think about what would make you happy.
As you are in school, I would highly recommend joining student organizations and applying for internships. These will both help you network and put into practice what you have learned. They should both give you an insight to what it could possibly look like working in any of your desired fields. Some might be harder than others to get an internship for, such as acting. But I think you should put yourself out there and try to learn as much as you about each career so you can make the best decision for you and your future.
- List what you value and look for in your career (work life balance, pursue passion, stability, etc.)
- Take classes related to the careers you are interested in pursuing (i.e. law class, theater class)
- Shadow or intern at a law firm, theater/acting company, school
- Network with lawyers, actors, and teachers by sitting down with them and asking questions about their studies and careers (try to find a contact through friends and loved ones that you can trust)
Hope you find these tips helpful!