Being a WR, you need to be explosive. Explosive in everything you do. Whether it is blocking, your burst off the line, your releases, the breaks on your route or the burst after the catch. Everything needs to be explosive. So you should be training to improve just that.
Now I’m not saying go against your high schools strength program. If you guys have a summer program set, stick to that. You want to be a team guy first, but this is the work you should be doing on your own. If you want to be explosive you need to work explosive movements. Power cleans, jump squats, pause squats, plyometrics, and etc. Now lifting super heavy is not going to get much accomplished in these lifts for WRs, don’t get me wrong, you want to be strong and that would help your strength but for explosion it should be about 75% of your max so you can focus on bar speed and exploding at the top of the movement. Explosive exercises work your fast twitch muscle fibers, which ties directly into explosiveness which is an all out effort movement. Training with these exercises are super important for any WR. Obviously you need to work other things like your grip and strength but these types of exercises I feel are essential. Staying in that 1-5 rep range is also crucial. You need to focus on being as explosive as possible. If you get into the 10-15 rep range you start to run out of gas and it’s more of a conditioning workout than an explosive workout working your fast twitch fibers.
Train for what you need. Train smart and hard. Good things will happen.