To echo what the above PP have said, these days to get into the most popular secondaries in St Albans you MUST be within catchment. It has nothing to do with "feeder" primaries. Beaumont and Sandringham are by far the most popular and their catchments are shrinking every year. Beaumont is getting especially tight with the big new housing developments springing up in the vicinity, eg. Kingsbury Gardens.
If you don't manage to bag a property near Beaumont, however, Samuel Ryder has an excellent reputation. It's also the only school where children can attend all the way through from nursery to secondary, so brilliant for stability and consistency. If you are towards the west/south west of the town centre you may be allocated Marlborough, which didn't have the best reputation when I was at school, over 20 years ago, but now also gets glowing reports. If you are north west you are probably looking at Townsend (mixed, CofE) or STAGS (all-girls). In the Fleetville area there's Verulam, which is all-boys, used to have an iffy reputation but has since come on in leaps and bounds apparently.
To be honest, there are no bad/undesirable secondaries in St Albans, but some are definitely more popular than others, and you will pay for your house accordingly. For a standard 3 bed semi with garden near Beaumont expect to pay (in the current market) an absolute minimum of around £750,000. Houses are snapped up within days, if not hours of going on the market. Not so sure about Sandringham but I imagine it's a similar situation. Good luck!