Hi Weedeb, don't have a huge amount of advice, just wanted to say hello! I live near-ish to ayr, DS is only 4 so a long way from the stage your children are at just now.
Ayr has some great schools and also a fantastic college which sometimes allows children to attend alongside what they are studying at school, depending on their interest.
I didn't go to school in Ayr but i went to a school not far away and used to attend the college on Tuesday afternoons for art classes, they also offered travel and tourism, hospitality and childcare, music and other things we wouldn't have had in school. Just something else to think about when considering education options for your older children.
As other posters have said Standard Grades begin in 3rd year (14/15) with exams held at the end of 4th year (15/16) up until then it's general education covering all subjects, then Children will pick what to study for Standard Grades. Intermediate 1, Intermediate 2 and Highers are offered for 5th and 6th year, depending on how well Standard Grades went, Children may spend 5th year at Intermediate 1 or 2 then progress to Highers in 6th year or may go straight into Highers in 5th year. Highers are also offered at college.
Hope this helped a little, as i said my son has a long way to go before he is at the stage your children are, and i left school in the area 8 years ago butbhopefully my knowledge is still relevant.
Good luck, i'll come back to your thread to see if there is
anything in particular you want to ask, i know the area well.