Memorizing the Quran requires both practice of new lessons and strong revision. Without revision, students may forget earlier lessons even if they are learning new portions regularly.
A simple Hifz plan should include a daily new lesson, recent revision, and old revision. Teacher monitoring is also important because mistakes can be corrected before they become habits.
Students should revise slowly, recite with Tajweed, and follow a routine that matches their capacity. Consistency is more valuable than rushing.