Ok. Speculation piece. But you have to bear with me, as usual, while I go off on a bit of a tangent.
Discovery learning has a number of features that its supporters would claim for it. One is that for a child to work something out for themselves means better learning than being told. Why might a teacher believe this to be true. One reason is that many adults work in that way. Take me and computers, as an example.
I have a new laptop and while much of how it works is the same as my previous now broken laptop one feature is not the same. My old laptop had two buttons just below the trackpad. One could click the left button or the right button to do different things. My new laptop has a bigger trackpad, nice, but NO buttons to click! So how was I to get a menu up? On my old laptop, the right button did that. I tried to click with two fingers on the trackpad (That should have worked I later learned but perhaps I am two fingers inept). Eventually, I resorted to reading the manual. I had to download it and read it ina PDF reader. I am quite happy to do that. It is the way the world works. I scanned the manual to find how to get a menu up and it was either two finger clicking, or hold the alt key and tap the trackpad. Worked fine. I will always remember how to get a menu up. Discovery learning!!! Super stuff.
But … most of what I discovered by discovery was stuff I already knew. The tiny amount that I resorted to the manual for, discovered myself in the manual, was in no way difficult. And because I needed the information and it was useful I learned it well.
Now think about a child who knows very little. The hurdles to their managing to learn via discovery are immense. How to find the manual and read it and also, perhaps, that manuals exist. But this is in an environment where they are not particularly literate in the stuff they are exploring. That, after all, is the purpose of school. To teach kids stuff they don’t yet know. If there is too much as yet unknown by the child discovery learning is torture. It just does not work. And it dramatically does not work for kids who are deemed disadvantaged. Possibly because their previous teachers tried discovery methods on them.