Perhaps think about how you might support at home to prep for the exams rather than tutor externally - parents can do so much without a tutor. Be realistc about strengths and weaknesses, print off papers, see what the content is, use bond books to help with comprehension practice and reasoning (or similar books - loads at whsmith and online sites to support reasoning), practice creative writing, practice description paragaphs, build their confidence, read, listen to audio books in the car for fun, figure out what exam technique they need to physically sit/complete the exam papers on the day - teach them how to take an exam, where are the gaps in their maths, practice breaking down complex maths questions into the component parts, read the question, answer the question asked, circle the key words on the exam paper/question to stay focused, do the easy questions first, breathe, check your work, edit your work, show your workings or you won’t get the marks, always always write your name on the exam paper, keep it light-hearted. Practice actual past papers the half-term before and build on the gaps you find. Listen to the radio, discuss current affairs themes, get relatives/family friends to chat with them at family get-togethers so they are talking to adults beyond mum and dad in advance of an interview.
Have done it 3 times without external tutors and have always been astounded at how guidance and help from parents can give them the boost needed to get over the finish line!