Apart from my sixth form I've never heard of another which needs business dress
generally the boys at our school wear suits - either black, blue or grey (from a range of places e.g. M + S, Next, house of fraiser, debenhams, asos, John Lewis and Burton)
Personally I like skinny suits and the ones at Topman are really nice but I would check before you buy them cause my school is very picky and changed the rules about certain things after everyone had bought stuff.
Lots of people care more about the style then what is practical so just wear whatever you think looks good on you and trust me some people spent hundreds of pounds on suits (unlike me who purchased from new look haha)
hope this helps
p.s for ties go to next in the sales cause they always have reduced stuff and they are nice silk ones :P