[T-Bird45]

You've gathered some pertinent background info but I'd say a critical piece is missing and that is the current teacher's input on whether the situation is salvageable to successfully complete the course with even a minimally-acceptable grade. If the answer is "NO," then you have a stronger case for the plan to drop to avoid the GPA impact from a failing grade on the transcript and remediate to prepare for re-enrollment in the course next year. Do not allow yourself to be manipulated by the school admin once it's determined the student cannot succeed and requires remediation. Student success and learning should be the only focus of the conversation, not their BS "rules."

If the teacher says "YES," then immediately put a remediation plan in place that includes Khan Academy on the areas that are causing problems. Based on what you wrote about the girl being unprepared for this level of work, I'd say the plan should include the basics of algebra and geometry before working actual Algebra II/Trig problems. Emphasize to the student that she is in a deep hole that will require great effort on her part to climb out of but show her the plan can succeed through dedication to do the work.

[Vendome]

Go with T-bird’s recommendation regarding “Kahn Academy”

I have a couple friends who had their kids utilize Kahn.

Both kids ended up at Ivy League skrewels.

One is at Cornell and I forget where the other is.