How can I get a better mark in the writing part of my Spanish GCSE/A-Level?

Firstly, it's important to have a bank of topic-specific vocab, which would demonstrate a wider and higher-register vocabulary level. During lessons, keep vocab lists of new words and arrange them by topic, such as the Environment, Holidays, and Home Life. Ensure you know the article for each noun you write down e.g "El medio ambiente", and not down if any verbs are irregular, e.g "ir". Secondly, prepare some sophisticated sentence structures that you're able to fit into many different topics, focusing in on offering solutions in the case of an argumentative essay, for example, "debemos hacer todo lo posible para..." "we must do all that is possible to...", or description in the case of describing a past event, e.g "Fui a.... con... y nos divertimos mucho en nuestro viaje" "I went to... with... and we enjoyed ourselves very much on this trip". With a bank of phrases such as this, it's possible to demonstrate a higher level of sophistication in your write and therefore obtain a higher grade.