DP over the top but that's the law
Other posters are quite right, as far as I understand it. Now our parent directory was launched in response to a parent who brought in her son's previous school's directory. Secondary school; each class photographed with form teacher; names, addresses, phone numbers and emails of all parents and teachers shown. This directory was used very heavily to manage and run events to support the school, and was publiched as a matter of course, supported by some parents advertising their companies or whatever. This of course is totally impossible here under the DPA, but the experience (in the USA) was, she explained, wholly positive.
What we've done is to get parents to sign a consent form; all that we disclose in the directory is that John Smith's parents and Mr Mike Smith and Miss Jane Jones, their phone number (landline or mobile to taste) and the area where they live. This seems to be sufficiently informative to be useful and sufficiently anonymised to do the job, with signed consent. The complaints we've had have been from parents who didn't sign the consent form and were therefore omitted! We get the data from the MIS (which also has the consent recorded), tidy it up, check it and then send that to the parents' association who actually print and distribute.
Seems to work. In anything like a sensible world I'd far prefer the US version.