Goku's line to Gohan during the Cell Games was about him becoming a scholar, at least in the original version. That's always been the profession that Gohan and the other characters talked about since the beginning of the series.
Once DBZ starts, Chichi's character is written to reflect the stereotype of the education-obsessed Asian mother, so that's part of the reason why Gohan is pushed in the "scholarly" direction. Gohan is also written in many ways to be an "anti-Goku". His language and speaking patterns are noticeably much more formal and polite (in the original) than Goku's, his intellect broader, and he's first introduced as a "sheltered crybaby" as opposed to the untamed and fearless Goku. Additionally, Chichi and Ox-King are both portrayed as being "country bumpkin" types themselves, even more so than Goku. So maybe part of Chichi's motivation for Gohan's education stems from her own background and desire for Gohan to not have to face that kind of social stigma, etc.
This was in the third DB movie, Mystical Adventure. It takes place in an alternate reality and is not canon to the series in any way.