I work on my school's website and when I create personas I find myself just going off of what I think. I know that is dangerous but I don't really have the time to go out and study the specific people we're trying to cater to. What can I do to get to know them without having to actually meet them. (For example, not all users are local students, there's parents of students, international/online students, etc.)
It's tough to design for someone you will never meet. I applaud the effort of creating personas despite the lack of access to users. I've been in this situation, too, and here is how I worked through it:
The project ended, because the focus of the client switched to a different product, but had I continued, I would have reached out to the bloggers and invited them to take part in an online evaluation of the design. That would have further refined the data I had passively collected about users, and provides the necessary access to users.
We as researchers are fortunate in that people share so much about their lives online. Students are avid users of social media. You may not be handed access to them directly, but if you get creative and search Twitter, Tumbl'r and Blogger for your school, you will find the very students and parents you seek. Then you can reach out to them, and build personas from real data.
I've been involved in persona projects thrice in my career as a UX Designer and two of those occasions were similar to your situation - limited funds.
Start somewhere Yes, it's not a good idea to just silo yourself and your thoughts when creating personas, but you have to realize that you have to start somewhere. If you can't afford a recruitment agency, you have to start by going off of your experience of past users of the website. If you have access to any analytics, it'll give you geographical insight as to where your users are coming from.
Remote interviews Get in touch with people you/the product owner thinks fit the bill of your target user. You'll find that people are quite happy to help most of the time. I used Skype to video conference them in and then, with their consent, used Screenium/QuickTime (you can also use a regular video camera and set it up) to record the sessions for review later. This costs no money. It's time-consuming, sure, but talking to people is the only way to get personas right. You can use website forums, social media to get through to people.
Variety I got in touch with a bunch of target users who were very different from each other. You already know there are some international students, local students, parents of students, etc. Try and get in touch with one of each kind of user you think you have.
Quick and Dirty Don't try and talk to 50 users. Do 5-10. You'll be amazed at how much you can learn.