The Scots fell behind in only the third minute at Bramall Lane when Nathan Redmond fired beyond goalkeeper Jordan Archer, and their misery piled up as Raheem Sterling, Connor Wickham, Ross Barkley, Jonjo Shelvey and Tom Carroll plundered more English goals.
It left Stark searching for answers and he said: "We were very poor, extremely poor in every sense, and it was a chastening experience.
"I think shock is probably the way we would describe it. Certainly we didn't see that coming, and by that I don't just mean the result, I mean the way the game panned out.
"We gave the ball away cheaply, we gave away cheap goals and against quality opposition you are always going to be punished. We failed to compete.
"We got caught a wee bit like a rabbit in the headlights to be honest with you. We were outmuscled, second to everything and it was a poor night in every respect. We can always take positives from games, but it will take me a wee while to come up with positives from that."
That is nevertheless the challenge that is facing Stark, who has been in charge of the Scotland juniors since 2008.
The next match for his side - which is just as daunting - is a matter of weeks away, with the Scots due to face Holland in Nijmegen on September 5 in a European Championship qualifier.
There is work to do before then and Stark admitted the jolt of conceding early caused Scotland to wobble. Consequently, his players dipped in mood and he is worried about what he saw unfold.
He told the Scottish Football Association's YouTube channel: "We spoke before the game. When they (England) have got the likes of Redmond and Raheem Sterling, with the pace they have got - and their players were pretty lively in the middle of the park as well - one thing we didn't want to give away was a cheap goal over the top with people getting in behind us.
"That was the last thing we spoke about. But that is what happened with the first goal.
"So we took a psychological knock there and we were rocky.
"I thought the only spell for us was around midway through the first half when we settled in, we weren't giving up chances and we kept the ball.
"We still could have taken better decisions to go forward - we had some good play and then got negative and turned back when we should have been going forward.
"So they are things that indicate confidence having been sapped a wee bit."
Sterling slotted in England's second in the 38th minute when the ball deflected through to him in the area off Wickham from Redmond's flick.
Scotland's defence was almost powerless against England's bursts forward after that, and the overall lacklustre nature of the performance left Stark at a loss.
He said: "They are young boys. They have never let me down or the country down in terms of the games they have played before.
"After this, that is exactly what they will feel and we all feel like that, and there is no point in trying to hide from it."