Click on the little arrow next to your folder/label. Under the 'In label list:' part, select 'Show'. Now your folders appear all the time. Also, you can click the "More" at the bottom to expand it.

Why is that so hard?

EDIT: No really - why is it so hard? Better than 90% of the complaining on this page could be solved just by spending a few minutes going through settings, tweaking GMail to your liking. There's even a settings page where you can see all of your labels in one place, and set each folder to show/hide/show if unread. It's specifically designed for the parent's use case, and yet he pretends that it doesn't exist.