What is a decent amount of weight for a 17 year old girl to squat, leg press, and bench?

Depends on weight.

Standard strength chart for females can be found here. http://funadvice.com/r/15sdqenrset

If the link doesn’t show then I’ll type it out.

Adult Females - Bench Press

Body Weight Un-trained Novice Interm. Advanced Elite 97 49 63 73 94 116 105 53 68 79 102 124 114 57 73 85 109 133 123 60 77 90 116 142 132 64 82 95 122 150 148 70 90 105 135 165 165 76 97 113 146 183 181 81 104 122 158 192 198 88 112 130 167 205 199+ 92 118 137 177 217

Adult Females - Squat

Body Weight Un-trained Novice Interm. Advanced Elite 97 46 84 98 129 163 105 49 91 106 140 174 114 53 98 114 150 187 123 56 103 121 160 199 132 59 110 127 168 211 148 65 121 141 185 232 165 70 130 151 200 256 181 75 139 164 215 268 198 81 150 174 229 288 199+ 85 158 184 242 303

Adult Females - Deadlift

Body Weight Un-trained Novice Interm. Advanced Elite 97 57 105 122 175 232 105 61 114 132 189 242 114 66 122 142 200 253 123 70 129 151 211 263 132 74 137 159 220 273 148 81 151 176 241 295 165 88 162 189 258 319 181 94 174 204 273 329 198 101 187 217 284 349 199+ 107 197 229 297 364

Your Leg Press should be kind of in the middle between your Squat and Deadlift weight or slightly over, though that greatly depends on strength and other factors (flexibility, conditioning, etc.)

For me, majority of my lifts are in the Intermediate stage for men because I’ve been seriously training for more than a year so that’s normal. The only lift that in the Advanced standard is my Deadlift because I have a strong lower back and legs.