Can't have the kids voting

They're most likely to vote Democratic.

A judge declined to order South Carolina’s Department of Motor Vehicles (DMV) and State Election Commission (SEC) to register thousands of young voters whose registrations were mistakenly denied because they were not yet 18 when they registered but would be by Election Day. These voters will not be allowed to cast a ballot this November.

[...]

South Carolina law allows 17-year-olds who will be 18 by the next election, and otherwise eligible, to register to vote.

[...]

The Richland County judge called the requested relief “too drastic” and said it would “create disorder in the voting system.”

  Democracy Docket

Surely that can go to the Supreme Court on an expedited basis. States have the right to dictate the methods of voting, but not to disenfranchise voters.

Can they not allow same day registration?

The ACLU asked the court to suspend the voter registration deadline, direct the DMV to identify all impacted voters and order the SEC to add those voters to the rolls. They also asked for every impacted voter to be notified of their registration status.

Gods bless the ACLU.