Hi, Maple. You could so be talking about my DS2, also Yr8 - very similar child/situation.
Agree with Pimmpom that this is a 'funny age' (aren't they all??!) I have posted myself previously on the same subject. Yr8 is still fairly early days at secondary - I feel my lad is only in the last month or so beginning to settle in and gel a little better with a few boys, that's typical of him, he does take longer than some to adapt to new situations.
Depending on how your school works, may he be split/streamed in some or all of his classes so that he gets to meet a wider range of kids? I definitely think it is worth voicing your concerns to the school - tutor, HOY, etc. We did this, and I think it has been beneficial - they have found various little tasks/responsibilities for my Son which has helped his self-esteem and made him become a little more out-going. Perhaps your school may also be able to suggest some clubs or activities which he may like to go to but may not know about?
However, at the end of the day, if your DS is quiet by nature and has a loving, supportive home life then I am sure it will all work out for him eventually when he matures - my DS1 has certainly widened his outlook/social circle since he started his options in September and is now in completely different classes, subjects, etc. with probably more things in common with his classmates. I am hoping that the same thing happens for DS2 and that he too 'blossoms' over the next year or two.
Just a supportive post really, not much advice, but best wishes to you.
xxMFxx