。
You'll have to study more next year.
Literal
Next-year [topic-は] more study-not-must [emphasis-よ].
~なければいけない is the obligation form (parallel to ~なければならない) — 'must do X.' いけない is slightly more colloquial than ならない. もっと ('more') is a basic comparative adverb. The terminal よ targets a listener with informational emphasis.