OP, by “T20 schools” I assume you mean the schools ranked in the top 20 in USNWR’s “best national universities”. But those are not necessarily the top 20 CS schools (that list is mentioned in this post).
So, for example Georgia Tech is far higher ranked for CS than Yale or Harvard, although you’ll find GTech far lower in the national list.
Unfortunately though, if your kid is a current senior then it’s too late at many of these top public CS schools because they require an EA application.