Am I overreacting? Husband giving step son's teacher a gift

I found out my husband bought my step son's 5th grade teacher a target gift card and gave it to him to give to her. He said the reason was because my step son has always been really quiet and shy and since being in her class he comes home excited to tell him things about school. Last week at dinner my step son told us how his teacher had them use a VR headset to go on a virtual field trip to different biomes for science class. He's always coming home saying great things about his teacher and how much fun he's having and he's actually making straight A's. I'm even happy about that. I just don't feel comfortable with him giving his female teacher a gift. My husband thinks it's not a big deal because it's from my step son but she obviously knows he didn't buy her the gift card. She's also really pretty and younger than me.