From what I know, the high level scheduler decides which process is to be taken from backing store and placed into memory/ready queue, while the low level scheduler decides which process in the ready queue is executed by the CPU. If this is the case, which of the two schedulers actually use the scheduling algorithms (such as Round Roben, First Come First Serve,...)??
The short term scheduler or low level scheduler. Short term Schedulers are used to manage the ready queue of the computer. These are responsible for selecting the job based on which type of algorithm you are using.
If you are using priority based the it will allow a high priority process to go in running state while preempting the low priority process.
For round robin when ever the time quantum expires running process will come back to the ready state.
So here another major hand in hand component which work with short scheduler is Dispatcher his work is jo dispatch the process which chosen by the short term scheduler and to perform context Switching.
Context Switching need to perform so that old context or info. Of the currently preempted process can be save so that after completing its I/O operations or when ever it will get its chance to get execute. It will start from where it is preempted.