If his IQ is above 140 and his SAT is under 1100, there is probably some problem. Only 1/2 of 1% of the population is at 140 or above IQ, but 1100 is about 60th percentile on the SAT. That is a large disparity.
The problem is, the SAT is a reasoning test much like the Stanford-Binet IQ test. So that large a disparity doesn't really make sense.
The ACT is more of an academic achievement test. It isn't all that unusual to find disparity between an IQ test score and and achievement test score of two or more standard deviations - in fact, that is one of the indicators for a learning disability/special ed diagnosis.
But since the SAT is more like the IQ test, that much of a disparity isn't right. Are you sure about the IQ test score?