Boyfriend Judges My Parenting

My son has been grounded all week because he didn't do good on his algebra 2 test. While I was making lunch my boyfriend says me "I think you put too much pressure on him". I was obviously very offended. He's not a parent nor has he ever been a parent. He tells me I stress him out too much and that he can obviously tell my son has bad anxiety i told him when he gets a doctorate in psychology, then come talk to me about MY child's mental health. He's sitting here making me feel like a bad parent for having high expectations. My son knows what I expect from him so idk why he feels it's his business to get involved in my parenting.