My understanding, based on what DS has said, is that LSE students take pride in coming at the bottom of student satisfaction tables, so it becomes self fulfilling.
It is worth unpicking what might cause lower student satisfaction rates and whether those apply to your son.
St Andrews gets really high student satisfaction, as does Buckingham, but both Universities will only suit some.
Equally International students; London etc will affect LSE results, even though some students will prefer London to other cities or campuses. Also type of degree. I have heard LSE academics claim that economic and politics students are more questioning thus critical. And how hard is the degree? LSE degrees tend to be quite mathematical, so tough for those for whom maths does not come easily, but great for those who prefer maths to essays. It also helps to be a self-starter. Equally some places seem to expect students to work harder, or in the case of LSE the culture/student body is relatively hard working, so those who don't, risk failing one or more exams.
I disagree with Bubbles. DS knew several people who were unhappy at LSE and might have preferred to go to Warwick. DS was fine and probably would not have liked Warwick. The same will apply to Imperial. It is three/four important years in your DS' life, so he should think about what will suit him. (And ignore the Guardian!)