First thing is first: Cheating is bad. I do not advocate cheating, but instead recommend against it. If the teacher clears the memory, they clearly consider programs cheating.
However, I will still answer your question. To create a fake Ram cleared screen you will need to write a program using the text( and line( commands. This can take a lot of time, and teachers will most likely see right through it since most of them are not stupid. To prevent a program from being cleared with a ram reset, you could archive it. This is done by going to the memory management menu, then programs, scrolling down to the program you want to archive and then pressing enter; or by running the command "Archive prgmNAME" from the homescreen. This may not fool a teacher since they may check your programs page after the clear, and it would still appear there. Another way of preventing items from being deleted in a ram reset is to create a group, since groups are archived. To create a group you go to the memory menu, then groups, then creating a group. To recover your programs, you scroll over to ungroup and then select which group to recover. I also recommend the GroupTool application which allows you to recover specific programs from the group and hide groups so they can only be seen from GroupTool. The final way to protect your programs from a ram reset would be to remake them as an application. Most teachers that I have had do not check applications, but rather only check the programs menu.
You may want to use an application like DoorsCS7. It allows you to hide, archive, rename, and run programs all within the app. You can even run archived programs without unarchiving them. I myself used it until I entered high school where I realized that I should start actually learning formulas for when I went to college.