A coarse thread screw works best with particle board, if you do a google search you can find screws made specifically for particle board.

You'll want to drill a pilot hole when working near the edges, because as you've seen it can fracture rather easily.

If you need to drive the screws flush, then a flat head might be better than a bugle head, the bugle head can fracture the wood as it tries to bury itself in the board.

Mongo

The screws designed for that material are called conformat screws. They need predrilled holes, however.

From the looks of those pictures, I don't see much you can do to improve the desks. Adding braces means more screws that may just strip out.

Having seen the pics, these desks strike me as very light-duty, poor-quality items that shouldn't be in a school. You've got a variety of problems for which there's no one magic bullet. You can certainly patch them together somewhat, but getting "many years" more use out of them is not likely.

The material is particleboard with a melamine coating - not "laminate."

The "connector bolts" you referred to aren't bolts at all. The are a common type of knockdown fastener. Lee Valley carries them, so you can see a picture of the uninstalled fastener here. The post of each fastener is threaded into a barbed plastic insert that's simply pressed into an undersized hole. These fasteners assemble quickly and avoid having screw heads showing on the tops of the desks, but they aren't very strong. When they are pulled loose the barbed plastic fittings are likely to enlarge the once-undersized holes they're in; you can tap the posts back into their holes, but they'll loosen again fairy easily.

To make any real headway, assume that each desk will have to be completely disassembled and every compromised joint will have to be fixed somehow. The posts of the knockdown fittings should be tapped back into their holes or turned to screw them deeper into their plastic anchors. Screws that have stripped must be replaced with longer screws, with coarse threads, for which you'll need to drill pilot holes.

In the first picture you need to straighten everything out so that the vertical PB (particleboard) member isn't splayed away from the keyboard tray, and tighten up the loose fasteners where possible. Then you'll have to improve on the original design by adding something to keep the problem from recurring. My inclination would be to add a couple of triangular wood gussets between the desktop and the outer face of the vertical PB member that carries the keyboard tray slide.

In the second pic you might remove the desktop and try to get the posts of the knockdown fasteners appropriately seated by tapping them down or (maybe) turning them to thread them more deeply into their embedded plastic anchors. As mentioned above, they'll probably come loose again, and do so more easily the second time. In the long run you may have to drill down through the desktop and drive some screws into the legs. This may be an unappetizing thought but, done right, it could add a lot of strength.

It's harder to see what's going on in the third pic, but perhaps the keyboard tray falls in the student's lap because of the splaying shown in the first pic? Adding the gussets I described, to prevent the splaying, should address this problem as well.

In the last pic, where a chunk of the PB is gone, there's no way to put Humpty Dumpty back together the way he was originally. See if you can relocate the fastener that blew out to another, undamaged part of the edge.

Thanks everyone for your response and input. Jon, especially for your very detailed response. I will print out all your responses and take them to school and see if we can get them in better shape than they are now. Maybe we can get a little more time out of them.

Jan

I sell custom laminate furniture, so for anyone's reference here's a little more information. The melamine used on these desks is (for all intents and purposes) high-grade contact paper. It really has no structural integrity.

What you want (and need) is high pressure laminate. This is what a Formica countertop is made of. It has its own structure integrity so the kinds of wear you're seeing would not happen with our furniture. In addition, laminate furniture should be constructed of 3/4" thick boards. Drawer sides and bottoms can thinner, as can the back plate of a cabinet, but nothing else. Melamine can be used for interior surfaces like a drawer box but not exterior surfaces.

Anything with cam locks (the "connector bolts" you referred to) is a potential sign of trouble. Years ago we sold bookcases that used cam locks. We'd assemble them for our customers because we'd glue up all the boards as well, and add screws and staples where we could. Customers come to us from 20 and 25 years ago asking for more of those bookcases because they held up so well. Your desks have none of that extra reinforcement.

Like jon said this can be repaired. There must be a parent or someone who can be asked to do the work, and the materials won't be much. I'm in agreement with him on the first picture, and for the second picture, absolutely drive down some screws. For the last picture you can either attach a thin sheet of plywood to the bottom and fill in the gap with some filler, or cut a new board to replace that one. Good luck.

Thanks, mogator88, for your response. I believe that I can find some parents to help me.

I will check into getting some gussets to help with the support and also adding some glue where they meet.

Thanks, again everyone!
Jan

In the second photo, I would rotate the screws in the middle and rear bolt in the side panel counterclockwise and try to engage the pins that are connected to the top. Sometimes if those pins are not seated all the way into the top, or the bolt in the side is not positioned properly, they will not connect with each other. That should be a correctable situation. Good luck with the other issues.

Another option: Find someone with a plate joiner (aka biscuit cutter), buy a box of biscuits and bottle of glue and get rid of the KD fasteners.

Here is a link that might be useful: Sample plate joiner