Bit of a Conundrum

[PeteSB75]

So, after much soul searching and difficult days, I've decided I really don't like my job enough to justify staying in it. I need a career change. I've been following the money for too long, I need to do what is right for me, and what I think will make me the happiest.

I am taking the necessary steps to go back to school to get an education degree, to teach English. This is going to be a multi-year process, likely a year of prereqs and about 2 years of masters classes, followed by a student teaching stint.

So the real question is, when do I tell my current boss? It's going to be about three years before I am ready to leave, but during most of that time, I will be taking classes. Work will only pay for school if it is for advancement within a related business area, so a CS degree or an MBA would fly, but I'll be paying for this myself, as well as still having to pay mortgage, etc, so I don't want to lose my job before I am ready.