Targeted help - Writing

My kid’s ACT preparation process so far: I forced him to take a practice test, then we sat down together and went over all of his missed questions then we waited a week (crazy school schedule) and he’s taking a section each night.

The writing section second sitting was last night. I’ve categorized his misses in this test and the last. 80% of his missed questions concern either comma placement or verb tense agreement. If he were perfect in those sorts of questions he would be in Ivy territory on this section.

I would like to drill him on these subjects.

Can any of you recommend a source for more test questions that cover comma placement and/or verb tense agreement?

It seems like the English section in general covers grammatical stuff like this. I found a bunch of previously released Practice tests and my S19 is doing sections too.