The classes do seem a bit heavy. Our local ps used to do block scheduling 4 per semester, so eight per year. Could you do something similar? So the 4 online classes + piano. School through the summer with Math, Chemistry and English.
OR
A modified loop schedule...online classes plus 1 more subject per day + piano. Monday online classes, block of Chemistry and piano practice;Tuesday online classes, block of English and piano practice; Wednesday online classes, block of math and piano practice; rinse repeat. You would be covering two of the subjects twice per week. If you are doing literature reads for part of English that could carry over onto Saturday, so in theory you would cover two blocks of Chemistry, Math, and English a week.
Please ignore horrible grammar and run-on sentences from those offering advice on how to schedule English. :blushing: