Answer:
Mr. Reid's seventh grade students had a positive effect on his life.
Step-by-step explanation:
The difference between affect and effect is that affect is a verb – “to affect” – meaning to influence or have an impact on something, while effect is the noun – “an effect (a positive or a negative effect) is the result of being affected by something. In this case, effect would be grammatically correct to use for the sentence, since the students are the ones affecting his life.