The Summer Mathematical School in Paris is a great opportunity for math lovers between 16 and 20 years old. The lectures will be in English, and the application deadline is April 15. The cost is 400 euros, and financial aid is available. The speakers are experts in various fields of mathematics. To apply, you need to fill out a short form, solve some math problems, write a motivation letter, and have teachers submit recommendation letters. Check out https://msp.math.ens.fr/ for more details.