Class newsletters, notices for parents, municipal bulletins. Illustrations are used constantly in these documents, but being non-commercial does not mean anything goes. Here are the points that trip people up, in the order worth checking them.

"It is non-commercial, so it is fine" does not follow
Copyright law contains exceptions for non-profit, no-fee performances and similar uses, but they do not licence every reproduction of an image into a handout. Even for material issued by a school or a local authority, the asset site's terms still apply.
The good news is that many free asset sites explicitly permit school and public sector use. Reading the terms settles the question, so it is worth doing once before you start.
Check that print use is permitted
Some sites permit web use but treat print separately. Newsletters and bulletins are printed and handed out, so this matters. If the terms only mention "use on websites", print may not have been considered.
Watch for limits on print runs and distribution
Some sites cap the number of copies. School-wide or authority-wide distribution reaches large numbers quickly, so check whether a limit exists. If you expect to exceed it, either find another source or ask the site directly.

Check the resolution
An image that looks fine on screen can look coarse in print. If it will occupy roughly a quarter of the page, 1000 pixels or more is a reasonable guide. Small placements are far less demanding.
For documents printed in black and white, colours with similar brightness can become indistinguishable. If you are unsure, run a test print in greyscale first.
Avoid anything that points to a specific person
Because these documents are distributed widely, it is safer to avoid depictions that call a particular pupil, parent or member of staff to mind. Hairstyles, body shapes and personal items that happen to match a real person can be read as pointing at them.
Choose generic illustrations that do not single anyone out. Before distributing, also check that no school name, company logo or recognisable character has crept into the image.
Keep it easy to reuse
These documents are rebuilt every month or every year. Noting the file name and where you obtained each asset saves you searching again when you want a matching set next time. Keeping a local copy also protects you if the source site ever closes.
How Visual Hub handles this
Our terms explicitly permit use in printed materials such as flyers and posters, and no attribution is required. For the full conditions, including anything relating to print runs, see the Terms of Use.
We generate assets while avoiding anything that evokes real people, existing characters or company logos, and we cover school and public sector scenes such as entrance ceremonies, sports days, culture festivals, parent-teacher conferences, city hall service counters and traffic safety classes.