I think that keeping all options open within the field would be one notion that needs to be kept in mind. Indeed, while the desire to enter any field early is wonderful, it is important to keep your dreams fluid and not lock them too tightly into rigid roles. I would say that in deciding this field is the way for you to go, getting to know as much about it early on can only help you. If this is indeed a passion for you, as the earlier poster suggested, read up on it as much as possible. Voraciously gaining as much insight as possible into the field will allow you to have a better grasp of it as you enter it. At the same time, being able to sense some of the potential challenges in the field through both reading and talking with people who currently work in it will also help you to navigate your ways in this setting and in your achieving your dreams.
mkcapen1's comments are good. I want to add a couple of items.
You can find an entry-level job as what's called a "Psych Tech" with just a bachelor's degree in Psychology. That sort of job can give you a lot of valuable experience, but it probably won't be exclusively in the area of child psychology and may not be the sort of job that you'd want to have for your entire career.
The steps that I would identify are:
1. Learn about the similarities and differences between a social worker and a child psychologist, and learn the differences within each of those professions. What sorts of social workers are there? (mkcapen1 is right about the differences between having a bachelor's and a master's degree in Social Work; a higher level degree is the door to greater professional opportunities).
2. Explore ways to strengthen the skills that are most important to those sorts of jobs. Good reading and writing skills are certainly always good to have, but other skills -- such as interpersonal communication -- are probably at least as important.
3. Be willing to review and even reconsider your dream job. You're still very young and are in a position to try on any number of different hats. While you're learning about possible future professions, you'll probably come across wonderful opportunities and possibilities that you've never even considered before.
Read, read, and read. Write, write , and write some more. The first step that you need to follow is to apply yourself now in your classes. A good educational foundation will help you in the future.
If you want to be a social worker you will be able to find work with direct people contact at the Bachelor's level. However, if you want to do any testing or work in a clinical setting you would want to pursue a Masters degree.
Before you get into any kind of social work program ask if it is an accredited program. It is very important that you know this because you only want to attend an accredited program.
If you are interested in Psychology you are looking at having to obtain a Maser's degree to get into any people oriented work.
Talk with your school gidance counselor and ask her about college programs that provide education in your area of choice. Another good idea is to research colleges on the web.