My heart's not in it
Offering the wolves excuses and lies will only make them view you as being weak or uncooperative, reinforcing their Org-given perception that they dictate how your life is managed.
Quietly say to the "School Overseer" that you don't want to be given any more platform assignments for the time being. When he asks why not, just say your reasons are private & personal, and that you things to deal with - but thanks for asking and if things change, you'll let him know.
If confronted within weeks or months, simply repeat, "There's nothing I can discuss at the moment, but if things change, I'll come and talk to you."
They'll get the message!!
Just say you are not going to be available to do it......elder asks why....say personal reasons....he presses the issue....simply say nothing you need to know, personal reasons, please respect my privacy. End of conversation, walk away....chuckle to self and heave big sigh of relief.
The big problem is that you get conditioned to think you have to supply them with reasons or excuses when in reality you don't. What you opt to do is voluntary and if you do not want to do something the reason doesn't matter. You just choose not to volunteer.
I like the chuckle bit Tiki...
After six weeks of not attending meetings, what I said to the sole elder who came round to find out whether I had turned rabid apostate or not was, "It's just not for me".
In truth of course I had become a rabid apostate and was full of loathing for the Watchtower and anything associated with it and I was so glad to have no further truck with the slimy organisation.
It was then announced at the KH that I was no longer one of Jehovah's Witnesses which in retrospect was like a denunciation of my character to my children; that I was now on the devil's side. Also I have no doubt that the announcement served as vindication of my wife's triumph as a brain dead believer and martyr to the cause; which would gain her a lot of sympathy from the faithful. (insert vomit icon)
So WIT, I think that "my heart is not in it" is an honest and rational response and it does not play along with the JW game of blind, unthinking obedience. You are not obliged to elaborate on your reason to the elders.
Eventually it could also start a message which when repeated, will reach the GB and inform them that their religion is useless garbage.
It is very much to the point that millions of JW's hearts are not in their religion.
It's sad isn't it that as full grown adults who are volunteering their time to do something (like give a talk) cannot say they don't want to do it anymore without having to make up a load of stories and excuses as to why they don't. We've all been there, some have the courage to just walk away, for others it's so much harder. This is what it is to be in a cult... you have no freedom or choice like normal people do.
Tell yourself you have the right to choose what you do and don't do in your life and that you don't owe anyone a reason or explanation. It's very freeing!