Is disobeying one's parents regarding their command to study and excel considered a sin (haram)? And is it obligatory to obey them if they command one to achieve the highest grades, or is it sufficient to succeed with an average grade?

Filial piety is one of the greatest acts of drawing closer to Allah. Therefore, whatever is possible for a child to do to obey them and gain their pleasure, let him do it. It is obligatory to obey them in striving in studies if abandoning them causes them significant harm, and this is according to the child's capacity.