Being stressed out during senior year is inevitable, but as a parent you need to know the limits of that stress.
Health and well-being is the top priority. My daughter attended an impressive and extremely competitive school, but my recommendation for her was to take all the AP’s she could handle during junior year (she took 6: AP CalcBC, AP Chem, AP Eng Lit, AP Eng Lang, AP Micro Econ, AP Macro Econ)), and leave the post AP’s (seminars: English, Econ, and Multivariable Calc) for senior year (post AP’s are more complex, but required less work) plus AP Bio and AP Spanish Lit.
She started writing her essays during the summer before senior year. That helped a lot!
She had a very busy, but reasonable, first semester. She was nervous and had a lot to deal with, but it was manageable.