Grammar, Usage / [this day Mr. Jackson] - help with grammar on thesis statment [2]

I'm doing a narrative essay and we have to write about an event in our life but i was just wondering if this thesis is correct. I just need to know if the semi colon is right or if it should be a period. Another suggestions to make my thesis better are also welcome.

To this day Mr. Jackson is still one of my least favorite teachers, however, I need to thank him; without Mr. Jackson I never would have learned that through hard work and help from good people one can achieve anything.