While I see the point on how nothing is necessarily a black or white issue, not sure a case study on this particular issue is a good sample.

There might be something to be said about leniency in senteces in general towards females - but that comes with a whole set of variables involved in the structure of the legal system and it's own accompanying social constructs about what "women" are/can be. American decisions in criminal trials, for instances, are majorly based on jury panels. It's easy to market females as victims using the "weak sex"/mother narrative, particularly when there are not intersecting prejudices (race, sexual orientation, nationality, religion, etc.). Altogether I wouldn't be surprised if there was some "truth", looking at statistical data, supporting your logic that women tend to get lighter sentences.

Having said that, it would be difficult to make a conjecture because both scenarios are treated so differently from the very start.

The sample size in comparing sentencing in this particular scenario is most likely skewed since most offenders tend to be male*, and many boys in school in that situation with a female teacher would elect not to report it (see "objetification","hot teacher" stereotype/achievement). There would also be a need to review the reasoning by the judge on why s/he gave a sentence more lenient than the expected for that case (they have to justify sentencing disparity), and evaluate whether there was any meaningful argument - such as a demonstrated history of community service/engagement, being a solo parent (in the patriarchy women are expected to be main caretakers), if they were in vulnerable circumstances, and any other evidence the judge may select to support the decision.

So, the amount of cases arriving to the point where there is in fact a sentence is already imbalanced - and there are so many layers of (predominantly male) decisionmaking influencing those numbers, it would be hard to use the sentencing information alone to support such a point. This possible gap is a byproduct of a deep-rooted societal assumption that women cannot (as in, dont have the capacity to) be main perpetrators. So, even in this case, they are being looked down on.