Aren't twitter posts, you know, public by default ? What is the big deal if these students intended to share this information with everyone. Or did Pearson somehow played tricks to subvert their trust ?
An organisation should only collectthe information it needs to; it should not keep that information longer than it needs; it should be transparent about the information it gathers and the reason for doing so.
In this case a company is searching public information (reasonable) but using education databases to get contact info for the student (not reasonable). This is unreasonable because they should be using things like warrants to get addresses -- something with judicial oversight. The student's personal contact information should be protected from this kind of trawling.
It doesn't matter if the children made the information public. The company can't store it.
Thing is that neither twitter nor facebook do anything to prevent children using their networks, you know, data is very important, specially that data.