All Turbo C++ versions for MS-DOS or the later Windows 3.x versions are older than ISO C++ and have semantics that eventually changed across versions.
Then there is the whole point of them being MS-DOS/Windows 3.x products that run in modern computers with various degrees of success.
There are open source clones of graphics.h and conio.h, and any good teacher could prepare the class material so that the students wouldn't have attrition.
And it isn't just talk, I spent one year doing TA activities so I know how much it costs to prepare such student materials.
On top of that, regular old Qt is still one of the most fully featured GUI frameworks, QtQuick is mostly used for mobile and embedded, even though it also works on desktop. Lazarus or Tkinter aren't better choices for starters, I say as someone who used both.
But, even if you don't like Qt, QtCreator is still a great IDE. No need to keep using a Dosbox with Turbo C++.
(I'm an Indian that learned C++ in school using Turbo C++ 10 years ago.)
Outdated? The point of learning programming at that age is to understand the basics - functions / if / for / while, structs / classes, and pointers. All of those work the same in Turbo C++ or in the latest MSVC.
Sure learning C++ via Turbo C++ doesn't prepare the student for modern code that uses `<algorithm>` or `std::shared_ptr` (or `std` at all), but those can always be learned later. The basics are more important.
If anything, the fact that Turbo C++ came with graphics.h meant I could make screensavers like starfield and a visual sudoku solver by myself without any hassle. It made programming fun and was certainly part of the reason I'm a programmer today. I'm not even sure how I would do those with MSVC or gcc today, let alone 10 years ago. WinForms + GDI? SDL? Both are much more complicated than what I remember of graphics.h's API.
Edit: graphics.h was the header with the graphics API, not conio.h