If you are a professional teacher, meaning you already have a class of students, and would like to connect them with native speakers, send me an email to email@example.com. I will then make your account a teacher account. There are a couple of options for connecting your students with native speakers. FYI, I am not familiar with rules for k-12, and although it's a pretty tame site, I would certainly recommend a discussion with your students about privacy and connecting with people online.
Option 1. Have them do it outside of class. They sign up, create their own account and arrange to meet their partner(s). This is most suitable for older students at the level of intermediate or higher. You have to factor in unreliable partners/students, so I'd recommend giving them advanced notice and specify the number of exchanges over a given period of time. We usually say to do it once or twice a month, this way if there's a problem, they can reconnect or find someone else. English speakers should never have a problem finding partners. To keep track, you can have students write a blog post as a summary. It's also nice if they follow up by sending their partner a link to their post describing the exchange.
Option 2. Find a partner class. You have the Teacher Search option now on your left. Keep in mind logistics can be challenging with different time zones, class hours, lab or internet availability and expectations. Make sure you're clear about your capabilities and requirements at the beginning. You may want to also check out ePals.com if you're looking for class to class exchanges at the k-12 level.
Option 3. Schedule an event. This is what we use most for our courses at Dickinson College. It basically turns our traditional computer lab hour into conversational practice for each student with a native speaker. Instructions and more details are in the top menu. If you have a computer lab with Skype, you can invite native speakers to sign up to contact you and your students at a given time. Each of your students would then be matched up with an individual from the site who signed up, though you'll probably have some groups of three. If you'd like to do this, let me know and I'll walk you through the first one. Contact me at the email address above.
Language exchanges can have a very positive effect on the classroom. If you have other questions, send me an email.