Green practice ought always to be based on fact - or at least on reasonable probability as to fact. It is simply not good enough merely to cherish 'the planet' as a cuddly toy of the concerned middle class mind (rather as 'progress' was such a toy of the Victorians, rather as 'the working class' was the mental teddy bear of the intelligentsia of two generations ago). Green practice ought to be based not upon what feels green, not upon what is currently dear to green hearts, but upon careful factual assessment of what, sustainably, the planet can give to us and can take from us.
Epistemology is the attempted answer to the question - 'on what grounds can it properly be claimed that xyz is indeed the case?' (where xyz is any statement purporting to be factual). Nobody would expect ordinary pupils to gain much from formal tuition in epistemology but even the most ordinary pupils need to have it instilled in them that it is simply not good enough to do - what is done in every bar-room debate - it is simply not good enough to say the truth is that which I feel to be true or the truth is which I proclaim or the truth is that which authority requires me to assert. Everybody needs to understand that truth, or more usually probable truth, is identified only by sceptical resort to defensible criteria. Without some degree of epistemological discipline, the truth will elude us and our best intentions about 'the planet' may well be misguided. Greens have a necessary interest in pupils' critical abilities being developed.
As to ethics, it is simply not good enough to proclaim 'moral values' - and by implication to claim that other people are forever undermining those values. Ethics is the practical inquiry into how shared general values can be applied to concrete cases, how to deal with situations in which there are evidently competing moral imperatives. The big ethical question for greens is how can we reconcile the legitimate interests of contemporary people with the legitimate interests of near, and far, posterity? This problem cannot be tackled usefully by vague moralising; it has to be addressed by disciplined ethical inquiry. Again, ordinary pupils cannot be expected to benefit from formal studies in ethics but they should be made fully aware that 'the road to hell is paved with good intentions'. Ethics, like epistemology, is a matter of disciplined sceptical inquiry - not merely a matter of untutored intuition or of received wisdom.
Aesthetics - the reflection upon, and cultivation of, our sense of the beautiful - is quite basic to effective greenery. Our principal motivation, as greens, is our awareness that many aspects of the natural world, and many of our artefacts within that world, are valuable precisely because they can excite our sense of wonder at the beautiful. Without the aesthetic dimension we might as well not bother about anything else very much.
We can develop ideas about the three E's but we should be most careful not to force those ideas into any specific ideological pattern - political or religious or whatever. The three E's are our proper concern both as unique individuals and as particles of common humanity. Green educators ought to take careful note of that.