Complex sentence: Theoretically "if" the need is identified it is possible for students to go up in level later on, however this requires a lot of extra effort, motivation and time resulting in many students not to reach their full potential.
Split into simpler sentences: Theoretically "if" the need is identified it is possible for students to go up in level. However if changing level later on it may require a lot of extra effort, motivation and time resulting in many students not to reach their full potential.