With subsequent photographs, you are trying to achieve a match in tone and size of your first image.
Each lesson you print you will need to do test strips as the chemicals will have changed.
Make sure if you are going to print several prints in a lesson that you use only one side of the developing table and chemicals – don’t swap sides in a lesson
Make a test strip that includes areas of portrait subject and background (if doing portraiture) and foreground and background (if doing landscape)
Choose timings close to that used for your first image, for example if your first image was exposed for 7 seconds, chose 4,1,1,1 or 5,1,1,1 and use the card at the side of the developer to uncover the image either left to right or top to bottom
Develop, stop and fix. Compare it to the first photograph you took. Adjust your filters and timings until a test strip achieves the required tone.
Do a complete test strip using the timing you have found from your test strip to give you the image tone your require and check for a final time that it matches your first image
If it does, you are then ready to print a full size copy of your chosen image