There is only one state secondary school in Haslemere: Woolmer Hill. It is on the smaller side (only 850 pupils), and has no sixth form. Several years ago, Woolmer Hill was a school to avoid. I understand it is much better now and it has a recent Ofsted rating of "good".
Not far away in Liphook is Bohunt, which is well thought of, and used to be attended by many Haslemere children whose parents didn't want Woolmer Hill. It is much bigger (almost 1900 children, including 6th form) Ofsted rating is "outstanding" but the last inspection was in 2013.
In Farnham, All Hallows (Catholic) is well regarded. It has around 1400 pupils (including 6th form). Its ofsted rating is also "outstanding" but that report is also old (2014).
Farnham also has Weydon School, which has around 1650 pupils (no 6th form) and a recent "good" Ofsted rating.
Given your preference for a smaller school, and the fact that you are Catholic, I'd look at both All Hallows and Woolmer Hill.
Finally, there is a Catholic school in Guildford (St Peter's) that are very well thought of.