The Cosco Highback is a forward-facing-only carseat, and it's safest to keep kids rear-facing to at least age 2, ideally longer. In some states it's now the law that kids under 2 must be rear-facing.
So a Cosco Highback would not be a good choice. It's a lousy seat anyway because it won't get most kids to the point where they're ready for a booster and you'd have to buy another harnessed seat anyway (it has very low top harness slots).
Would you like recommendations for a suitable seat? If so, what is the child's height, and is there a specific budget in mind?