Esper question (0%?)

Haven’t played this game in 30 years and what a delight to re-find it, and this community. Question about espers: no matter how much I level up, it appears that some of the spells are stuck at 0%. For example (and pic related), the esper Siren is supposed to teach Fire, right? But no matter what I do, it’s stuck at 0%.

I don’t understand these mechanics any more than I did when I was 10, haha.