Nothing wrong* with hiring a transwoman.
Everything wrong with the transwoman demanding the children are taught they are a woman.
Children believe what adults tell them. That's why the concept of grooming exists. That's why they get recruited by nefarious regimes eg Hitler youth. Adults working with children hold a huge responsibility.
*Actually there is now something wrong with hiring any trans person to work with children. There is no compulsion for them to declare their past identity on a criminal record check and an employer would likely be too scared to ask (deadnaming is potentially a hate crime, as is letting slip you know what sex they are). So basically safeguarding and criminal record checks no longer work for trans people. THIS is actually transphobic, because they are receiving different treatment due to being trans. But sadly not the kind of transphobia that interests activists.