Question

Does this make sense? Then realizing that teachers will not give him or her candy every day when he or she behaves each and every time.

Answer 1

No it's a fragment sentence. All you have is one clause of what seems to be a cause and effect sentence. To complete the sentence you need another clause that explains the result of the "realizing". For example:

Then realizing that teachers will not give him or her candy every day when he or she behaves each and every time, he or she stops behaving altogether.

This is not really a very well formed sentence, but at least now it is complete.