I think you're right. I tried a new game of Troublemaker Scenario with High School Years disabled, and neither the fear nor the Must Pay Attention tense moodlet showed up the first day. When you have a D or F and join High School, you get the moodlet when you arrive at school, and lose it about lunch time.
Just tried another new try at the scenario (with HSY enabled) and couldn't ask Rita for extra credit with the fear in the lady's room. I suspect both you and the teacher need to be in the classroom to get the option.
The fear clears as soon as you start the extra credit. You don't need to even start homework before asking for extra credit, but do need the fear, which usually triggers well after the end of afternoon class, when ordinarily the teen would have already gone home or to extracurricular activities. If the timing of the fear triggering could be tweaked to consistently trigger during afternoon class I think it would be much better.
A couple more issues I've noticed that you might want to split off:
1) You don't lose grade progress when you join, even if you skip both classes and all tasks. Sending alone can cause you to lose grade progress if you choose to Make Friends or Slack Off during the school day.
2) Grade progress gain is slower when you Join than when you Send Alone, and seems to only increase from completing tasks at school. Doing homework (regular, extra credit or make up homework) does not seem to affect progress at all. My teen took 4 days to get promoted from F to D Joining every day. In my opinion there should be an effect on progress at the beginning of the school day depending on how much homework was completed.
