My boyfriend family doesn't think I am a good choice financially

My boyfriend just got a job as one of John Deere chemical engineers. I am a preschool teacher. My boyfriends family feels that as a preschool teacher I am not a financially good investment.  they don't believe that it will get me far in life as I won't be able to financially support a potential family as much as he would. They think that he and I should be on the same financial playing field. I am worried that their opinion of me will effect our relationship moving forward . How do I Handel his families disapproval of me. They gave him an altimatum which is  I get a better paying job or they end it. I feel so disrespected by his family.
We have been together for 3 years during those three years me and my family supported him while he was looking for a job. His family basically disowned him as their son. They had nothing positive to say about him. They blamed their failing marriage on him and told him that he was going to make nothing of himself. I watched him stuggle to find work to the point that I was worried about his mental well being. His parents wanted nothing to do with him until he started making big money. How am I supposed embrace his family when they think lowly of me and value their son based off of his financial gain. I have loved him with or with out a job and to them it is not enough. 
I feel that in our future I will be able to give more to a family than financial gains. Up until his family stepped back into his life and showed him some attention and respect I felt that we were on the same page. Now I don't know which way is up. He use to hate the fact that his parents are both workaholics and thought so highly of money. Now he is starting to sound just like them. I am worried that he is letting his family's opinions over ride his own. And I really don't want to lose him over money.