There are only a few testers who find any value in this extremely out-of-date test, and that value is only after taking another test and hitting ceilings (and so maybe figuring out more details about particular strengths). I don't think I've heard of anyone using the LM as a starter IQ test. I would indeed imagine that many people today could get very high scores on that. In fact, I'm sure you could probably find old copies of it if you looked around.
But beyond that, how is this child doing in achievement? I wouldn't worry about the score drop if he seems to be doing well academically. Does his profile fit more with a highly gifted kid? Then don't worry about numbers.
