Explanation:

- The average marks for 30 boys is 88. Therefore, the total marks for all 30 boys is $30\times 88=2640$.

- When the top two scores are excluded, the average of the remaining 28 boys is 87.5, so the total for 28 boys is $28\times 87.5=2450$.

- The sum of the top two scores is $2640-2450=190$.

- If the top two scores differ by 2, let's say the scores are $x$ and $x-2$.

- Solving $x+(x-2)=190$, we get $2x-2=190$, which simplifies to $2x=192$ and thus $x=96$.

- The highest mark is 96.