Option 1: The statement "All dancers are boys" is not necessarily true. While we know that all boys are dancers, it doesn`t imply that all dancers must be boys. There could be other individuals (such as girls) who are also dancers.

Option 2: The statement "All boys are students" is not necessarily true. While it is given that all students are boys, it doesn`t imply that all boys must be students. There could be boys who are not students.

Option 3: The statement "All dancers are students" is not necessarily true. While it is given that all students are boys and all boys are dancers, it doesn`t necessarily mean that all dancers must be students. There could be individuals who are dancers but not students.

Option 4: The statement "All students are dancers" is definitely true based on the given information. It is stated that all students are boys and all boys are dancers. Therefore, it can be concluded that all students must also be dancers.

In conclusion, the correct statement is option 4.