How can partners with AS genotype make babies that are not SS?

Dad AS, Mum AS. Let’s work it out

A from Dad:

A from Mom AA

S from Mom AS

S from Dad:

A from Mom: AS

S from Dad: SS

That is the beginnings of your answer- you have a 75% chance kid is not SS.

You can stop here if you wish.

If you want to be scientifically technical, at time of writing, you can go embryo implantation with preimplantation genetic diagnosis (PGD), involves removing a cell from an IVF embryo to test it for a specific genetic condition (cystic fibrosis the most common example) before transferring the embryo to the uterus.