In general, if you test a SQL query in SQL Developer against your PowerSchool database, that same SQL query should work in a PowerSchool custom page using ~[tlist_sql][/tlist_sql]. It does not, however—I discovered just now—work if you include a REGEXP_LIKE as part of your query. Will work fine in SQL Developer… just not in a PowerSchool custom page.
Unfortunately, the only workaround I had was to fetch more results than I wanted server side and then use jQuery on the client side to filter out the extraneous results.
Update: Apparently, REGEXP_LIKE does work with ~[tlist_sql], or so I hear from someone with a lot more PowerSchool experience than I have. I thought I was being careful with my syntax, but it’s possible I just screwed up, and SQL Developer is more forgiving of punctuation mistakes than ~[tlist_sql] is.